Accessing data based on a dispersed storage network rebuilding issue

ABSTRACT

A method begins by a set of storage units of a dispersed storage network (DSN) storing a plurality of encoded data slices, where each storage unit stores a unique sub-set of encoded data slices. The method continues with each storage unit dispersed storage error encoding at least a recovery threshold number of encoded data slices to produce a local set of encoded recovery data slices. In response to a retrieval request, the method continues with a device identifying a storage unit of an initial recovery number of storage units having a rebuilding issue and determining whether the rebuilding issue is correctable at a DSN level. When the rebuilding issue is correctable at the DSN level the method continues with the device selecting another storage unit to replace the storage unit to produce a recovery number of storage units and sending retrieve requests to the recovery number of storage units.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. § 119(e) to U.S. Provisional Application No. 62/008,182,entitled “UTILIZING LOCAL REDUNDANCY IN A DISPERSED STORAGE NETWORK”,filed Jun. 5, 2014, which is hereby incorporated herein by reference inits entirety and made part of the present U.S. Utility PatentApplication for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION

Technical Field of the Invention

This invention relates generally to computer networks and moreparticularly to dispersed storage of data and distributed taskprocessing of data.

Description of Related Art

Computing devices are known to communicate data, process data, and/orstore data. Such computing devices range from wireless smart phones,laptops, tablets, personal computers (PC), work stations, and video gamedevices, to data centers that support millions of web searches, stocktrades, or on-line purchases every day. In general, a computing deviceincludes a central processing unit (CPU), a memory system, userinput/output interfaces, peripheral device interfaces, and aninterconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using“cloud computing” to perform one or more computing functions (e.g., aservice, an application, an algorithm, an arithmetic logic function,etc.) on behalf of the computer. Further, for large services,applications, and/or functions, cloud computing may be performed bymultiple cloud computing resources in a distributed manner to improvethe response time for completion of the service, application, and/orfunction. For example, Hadoop is an open source software framework thatsupports distributed applications enabling application execution bythousands of computers.

In addition to cloud computing, a computer may use “cloud storage” aspart of its memory system. As is known, cloud storage enables a user,via its computer, to store files, applications, etc. on an Internetstorage system. The Internet storage system may include a RAID(redundant array of independent disks) system and/or a dispersed storagesystem that uses an error correction scheme to encode data for storage.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a distributedcomputing system in accordance with the present invention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a diagram of an example of a distributed storage and taskprocessing in accordance with the present invention;

FIG. 4 is a schematic block diagram of an embodiment of an outbounddistributed storage and/or task (DST) processing in accordance with thepresent invention;

FIG. 5 is a logic diagram of an example of a method for outbound DSTprocessing in accordance with the present invention;

FIG. 6 is a schematic block diagram of an embodiment of a dispersederror encoding in accordance with the present invention;

FIG. 7 is a diagram of an example of a segment processing of thedispersed error encoding in accordance with the present invention;

FIG. 8 is a diagram of an example of error encoding and slicingprocessing of the dispersed error encoding in accordance with thepresent invention;

FIG. 9 is a diagram of an example of grouping selection processing ofthe outbound DST processing in accordance with the present invention;

FIG. 10 is a diagram of an example of converting data into slice groupsin accordance with the present invention;

FIG. 11 is a schematic block diagram of an embodiment of a DST executionunit in accordance with the present invention;

FIG. 12 is a schematic block diagram of an example of operation of a DSTexecution unit in accordance with the present invention;

FIG. 13 is a schematic block diagram of an embodiment of an inbounddistributed storage and/or task (DST) processing in accordance with thepresent invention;

FIG. 14 is a logic diagram of an example of a method for inbound DSTprocessing in accordance with the present invention;

FIG. 15 is a diagram of an example of de-grouping selection processingof the inbound DST processing in accordance with the present invention;

FIG. 16 is a schematic block diagram of an embodiment of a dispersederror decoding in accordance with the present invention;

FIG. 17 is a diagram of an example of de-slicing and error decodingprocessing of the dispersed error decoding in accordance with thepresent invention;

FIG. 18 is a diagram of an example of a de-segment processing of thedispersed error decoding in accordance with the present invention;

FIG. 19 is a diagram of an example of converting slice groups into datain accordance with the present invention;

FIG. 20 is a diagram of an example of a distributed storage within thedistributed computing system in accordance with the present invention;

FIG. 21 is a schematic block diagram of an example of operation ofoutbound distributed storage and/or task (DST) processing for storingdata in accordance with the present invention;

FIG. 22 is a schematic block diagram of an example of a dispersed errorencoding for the example of FIG. 21 in accordance with the presentinvention;

FIG. 23 is a diagram of an example of converting data into pillar slicegroups for storage in accordance with the present invention;

FIG. 24 is a schematic block diagram of an example of a storageoperation of a DST execution unit in accordance with the presentinvention;

FIG. 25 is a schematic block diagram of an example of operation ofinbound distributed storage and/or task (DST) processing for retrievingdispersed error encoded data in accordance with the present invention;

FIG. 26 is a schematic block diagram of an example of a dispersed errordecoding for the example of FIG. 25 in accordance with the presentinvention;

FIG. 27 is a schematic block diagram of an example of a distributedstorage and task processing network (DSTN) module storing a plurality ofdata and a plurality of task codes in accordance with the presentinvention;

FIG. 28 is a schematic block diagram of an example of the distributedcomputing system performing tasks on stored data in accordance with thepresent invention;

FIG. 29 is a schematic block diagram of an embodiment of a taskdistribution module facilitating the example of FIG. 28 in accordancewith the present invention;

FIG. 30 is a diagram of a specific example of the distributed computingsystem performing tasks on stored data in accordance with the presentinvention;

FIG. 31 is a schematic block diagram of an example of a distributedstorage and task processing network (DSTN) module storing data and taskcodes for the example of FIG. 30 in accordance with the presentinvention;

FIG. 32 is a diagram of an example of DST allocation information for theexample of FIG. 30 in accordance with the present invention;

FIGS. 33-38 are schematic block diagrams of the DSTN module performingthe example of FIG. 30 in accordance with the present invention;

FIG. 39 is a diagram of an example of combining result information intofinal results for the example of FIG. 30 in accordance with the presentinvention;

FIGS. 40A and 40B are a schematic block diagram of an embodiment of adispersed storage network (DSN) in accordance with the presentinvention;

FIG. 40C is a flowchart illustrating an example of accessing data inaccordance with the present invention;

FIGS. 41A and 41B are a schematic block diagram of another embodiment ofa dispersed storage network (DSN) in accordance with the presentinvention;

FIG. 41C is a flowchart illustrating an example of storing an encodeddata slice in accordance with the present invention;

FIG. 42A is a schematic block diagram of another embodiment of adispersed storage network (DSN) in accordance with the presentinvention;

FIG. 42B is a flowchart illustrating an example of storing localredundancy in accordance with the present invention;

FIG. 43 is a flowchart illustrating another example of storing localredundancy in accordance with the present invention;

FIGS. 44A-44C are schematic block diagrams of another embodiment of adispersed storage network (DSN) in accordance with the presentinvention;

FIG. 44D is a flowchart illustrating another example of accessing databased on a dispersed storage network (DSN) rebuilding issue inaccordance with the present invention;

FIG. 45A is a schematic block diagram of another embodiment of adispersed storage and task (DST) execution (EX) unit 36 in accordancewith the present invention;

FIG. 45B is a flowchart illustrating an example of rebuilding andencoded data slice in accordance with the present invention;

FIG. 46A is a schematic block diagram of another embodiment of adispersed storage network (DSN) in accordance with the presentinvention;

FIG. 46B is a flowchart illustrating an example of brokering selectionof a dispersed storage network (DSN) in accordance with the presentinvention;

FIG. 47A is a schematic block diagram of another embodiment of adispersed storage network (DSN) in accordance with the presentinvention;

FIG. 47B is a flowchart illustrating an example of another rebuilding anencoded data slice in accordance with the present invention;

FIGS. 48A-B are a schematic block diagram of another embodiment of adispersed storage network (DSN) in accordance with the presentinvention; and

FIG. 48C is a flowchart illustrating an example of reliably recoveringstored data in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a distributedcomputing system 10 that includes a user device 12 and/or a user device14, a distributed storage and/or task (DST) processing unit 16, adistributed storage and/or task network (DSTN) managing unit 18, a DSTintegrity processing unit 20, and a distributed storage and/or tasknetwork (DSTN) module 22. The components of the distributed computingsystem 10 are coupled via a network 24, which may include one or morewireless and/or wire lined communication systems; one or more privateintranet systems and/or public internet systems; and/or one or morelocal area networks (LAN) and/or wide area networks (WAN).

The DSTN module 22 includes a plurality of distributed storage and/ortask (DST) execution units 36 that may be located at geographicallydifferent sites (e.g., one in Chicago, one in Milwaukee, etc.). Each ofthe DST execution units is operable to store dispersed error encodeddata and/or to execute, in a distributed manner, one or more tasks ondata. The tasks may be a simple function (e.g., a mathematical function,a logic function, an identify function, a find function, a search enginefunction, a replace function, etc.), a complex function (e.g.,compression, human and/or computer language translation, text-to-voiceconversion, voice-to-text conversion, etc.), multiple simple and/orcomplex functions, one or more algorithms, one or more applications,etc.

Each of the user devices 12-14, the DST processing unit 16, the DSTNmanaging unit 18, and the DST integrity processing unit 20 include acomputing core 26 and may be a portable computing device and/or a fixedcomputing device. A portable computing device may be a social networkingdevice, a gaming device, a cell phone, a smart phone, a personal digitalassistant, a digital music player, a digital video player, a laptopcomputer, a handheld computer, a tablet, a video game controller, and/orany other portable device that includes a computing core. A fixedcomputing device may be a personal computer (PC), a computer server, acable set-top box, a satellite receiver, a television set, a printer, afax machine, home entertainment equipment, a video game console, and/orany type of home or office computing equipment. User device 12 and DSTprocessing unit 16 are configured to include a DST client module 34.

With respect to interfaces, each interface 30, 32, and 33 includessoftware and/or hardware to support one or more communication links viathe network 24 indirectly and/or directly. For example, interface 30supports a communication link (e.g., wired, wireless, direct, via a LAN,via the network 24, etc.) between user device 14 and the DST processingunit 16. As another example, interface 32 supports communication links(e.g., a wired connection, a wireless connection, a LAN connection,and/or any other type of connection to/from the network 24) between userdevice 12 and the DSTN module 22 and between the DST processing unit 16and the DSTN module 22. As yet another example, interface 33 supports acommunication link for each of the DSTN managing unit 18 and DSTintegrity processing unit 20 to the network 24.

The distributed computing system 10 is operable to support dispersedstorage (DS) error encoded data storage and retrieval, to supportdistributed task processing on received data, and/or to supportdistributed task processing on stored data. In general and with respectto DS error encoded data storage and retrieval, the distributedcomputing system 10 supports three primary operations: storagemanagement, data storage and retrieval (an example of which will bediscussed with reference to FIGS. 20-26), and data storage integrityverification. In accordance with these three primary functions, data canbe encoded, distributedly stored in physically different locations, andsubsequently retrieved in a reliable and secure manner. Such a system istolerant of a significant number of failures (e.g., up to a failurelevel, which may be greater than or equal to a pillar width minus adecode threshold minus one) that may result from individual storagedevice failures and/or network equipment failures without loss of dataand without the need for a redundant or backup copy. Further, the systemallows the data to be stored for an indefinite period of time withoutdata loss and does so in a secure manner (e.g., the system is veryresistant to attempts at hacking the data).

The second primary function (i.e., distributed data storage andretrieval) begins and ends with a user device 12-14. For instance, if asecond type of user device 14 has data 40 to store in the DSTN module22, it sends the data 40 to the DST processing unit 16 via its interface30. The interface 30 functions to mimic a conventional operating system(OS) file system interface (e.g., network file system (NFS), flash filesystem (FFS), disk file system (DFS), file transfer protocol (FTP),web-based distributed authoring and versioning (WebDAV), etc.) and/or ablock memory interface (e.g., small computer system interface (SCSI),internet small computer system interface (iSCSI), etc.). In addition,the interface 30 may attach a user identification code (ID) to the data40.

To support storage management, the DSTN managing unit 18 performs DSmanagement services. One such DS management service includes the DSTNmanaging unit 18 establishing distributed data storage parameters (e.g.,vault creation, distributed storage parameters, security parameters,billing information, user profile information, etc.) for a user device12-14 individually or as part of a group of user devices. For example,the DSTN managing unit 18 coordinates creation of a vault (e.g., avirtual memory block) within memory of the DSTN module 22 for a userdevice, a group of devices, or for public access and establishes pervault dispersed storage (DS) error encoding parameters for a vault. TheDSTN managing unit 18 may facilitate storage of DS error encodingparameters for each vault of a plurality of vaults by updating registryinformation for the distributed computing system 10. The facilitatingincludes storing updated registry information in one or more of the DSTNmodule 22, the user device 12, the DST processing unit 16, and the DSTintegrity processing unit 20.

The DS error encoding parameters (e.g., or dispersed storage errorcoding parameters) include data segmenting information (e.g., how manysegments data (e.g., a file, a group of files, a data block, etc.) isdivided into), segment security information (e.g., per segmentencryption, compression, integrity checksum, etc.), error codinginformation (e.g., pillar width, decode threshold, read threshold, writethreshold, etc.), slicing information (e.g., the number of encoded dataslices that will be created for each data segment); and slice securityinformation (e.g., per encoded data slice encryption, compression,integrity checksum, etc.).

The DSTN managing unit 18 creates and stores user profile information(e.g., an access control list (ACL)) in local memory and/or withinmemory of the DSTN module 22. The user profile information includesauthentication information, permissions, and/or the security parameters.The security parameters may include encryption/decryption scheme, one ormore encryption keys, key generation scheme, and/or dataencoding/decoding scheme.

The DSTN managing unit 18 creates billing information for a particularuser, a user group, a vault access, public vault access, etc. Forinstance, the DSTN managing unit 18 tracks the number of times a useraccesses a private vault and/or public vaults, which can be used togenerate a per-access billing information. In another instance, the DSTNmanaging unit 18 tracks the amount of data stored and/or retrieved by auser device and/or a user group, which can be used to generate aper-data-amount billing information.

Another DS management service includes the DSTN managing unit 18performing network operations, network administration, and/or networkmaintenance. Network operations includes authenticating user dataallocation requests (e.g., read and/or write requests), managingcreation of vaults, establishing authentication credentials for userdevices, adding/deleting components (e.g., user devices, DST executionunits, and/or DST processing units) from the distributed computingsystem 10, and/or establishing authentication credentials for DSTexecution units 36. Network administration includes monitoring devicesand/or units for failures, maintaining vault information, determiningdevice and/or unit activation status, determining device and/or unitloading, and/or determining any other system level operation thataffects the performance level of the system 10. Network maintenanceincludes facilitating replacing, upgrading, repairing, and/or expandinga device and/or unit of the system 10.

To support data storage integrity verification within the distributedcomputing system 10, the DST integrity processing unit 20 performsrebuilding of ‘bad’ or missing encoded data slices. At a high level, theDST integrity processing unit 20 performs rebuilding by periodicallyattempting to retrieve/list encoded data slices, and/or slice names ofthe encoded data slices, from the DSTN module 22. For retrieved encodedslices, they are checked for errors due to data corruption, outdatedversion, etc. If a slice includes an error, it is flagged as a ‘bad’slice. For encoded data slices that were not received and/or not listed,they are flagged as missing slices. Bad and/or missing slices aresubsequently rebuilt using other retrieved encoded data slices that aredeemed to be good slices to produce rebuilt slices. The rebuilt slicesare stored in memory of the DSTN module 22. Note that the DST integrityprocessing unit 20 may be a separate unit as shown, it may be includedin the DSTN module 22, it may be included in the DST processing unit 16,and/or distributed among the DST execution units 36.

To support distributed task processing on received data, the distributedcomputing system 10 has two primary operations: DST (distributed storageand/or task processing) management and DST execution on received data(an example of which will be discussed with reference to FIGS. 3-19).With respect to the storage portion of the DST management, the DSTNmanaging unit 18 functions as previously described. With respect to thetasking processing of the DST management, the DSTN managing unit 18performs distributed task processing (DTP) management services. One suchDTP management service includes the DSTN managing unit 18 establishingDTP parameters (e.g., user-vault affiliation information, billinginformation, user-task information, etc.) for a user device 12-14individually or as part of a group of user devices.

Another DTP management service includes the DSTN managing unit 18performing DTP network operations, network administration (which isessentially the same as described above), and/or network maintenance(which is essentially the same as described above). Network operationsinclude, but are not limited to, authenticating user task processingrequests (e.g., valid request, valid user, etc.), authenticating resultsand/or partial results, establishing DTP authentication credentials foruser devices, adding/deleting components (e.g., user devices, DSTexecution units, and/or DST processing units) from the distributedcomputing system, and/or establishing DTP authentication credentials forDST execution units.

To support distributed task processing on stored data, the distributedcomputing system 10 has two primary operations: DST (distributed storageand/or task) management and DST execution on stored data. With respectto the DST execution on stored data, if the second type of user device14 has a task request 38 for execution by the DSTN module 22, it sendsthe task request 38 to the DST processing unit 16 via its interface 30.An example of DST execution on stored data will be discussed in greaterdetail with reference to FIGS. 27-39. With respect to the DSTmanagement, it is substantially similar to the DST management to supportdistributed task processing on received data.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (IO)controller 56, a peripheral component interconnect (PCI) interface 58,an IO interface module 60, at least one IO device interface module 62, aread only memory (ROM) basic input output system (BIOS) 64, and one ormore memory interface modules. The one or more memory interfacemodule(s) includes one or more of a universal serial bus (USB) interfacemodule 66, a host bus adapter (HBA) interface module 68, a networkinterface module 70, a flash interface module 72, a hard drive interfacemodule 74, and a DSTN interface module 76.

The DSTN interface module 76 functions to mimic a conventional operatingsystem (OS) file system interface (e.g., network file system (NFS),flash file system (FFS), disk file system (DFS), file transfer protocol(FTP), web-based distributed authoring and versioning (WebDAV), etc.)and/or a block memory interface (e.g., small computer system interface(SCSI), internet small computer system interface (iSCSI), etc.). TheDSTN interface module 76 and/or the network interface module 70 mayfunction as the interface 30 of the user device 14 of FIG. 1. Furthernote that the IO device interface module 62 and/or the memory interfacemodules may be collectively or individually referred to as IO ports.

FIG. 3 is a diagram of an example of the distributed computing systemperforming a distributed storage and task processing operation. Thedistributed computing system includes a DST (distributed storage and/ortask) client module 34 (which may be in user device 14 and/or in DSTprocessing unit 16 of FIG. 1), a network 24, a plurality of DSTexecution units 1-n that includes two or more DST execution units 36 ofFIG. 1 (which form at least a portion of DSTN module 22 of FIG. 1), aDST managing module (not shown), and a DST integrity verification module(not shown). The DST client module 34 includes an outbound DSTprocessing section 80 and an inbound DST processing section 82. Each ofthe DST execution units 1-n includes a controller 86, a processingmodule 84, memory 88, a DT (distributed task) execution module 90, and aDST client module 34.

In an example of operation, the DST client module 34 receives data 92and one or more tasks 94 to be performed upon the data 92. The data 92may be of any size and of any content, where, due to the size (e.g.,greater than a few Terabytes), the content (e.g., secure data, etc.),and/or task(s) (e.g., MIPS intensive), distributed processing of thetask(s) on the data is desired. For example, the data 92 may be one ormore digital books, a copy of a company's emails, a large-scale Internetsearch, a video security file, one or more entertainment video files(e.g., television programs, movies, etc.), data files, and/or any otherlarge amount of data (e.g., greater than a few Terabytes).

Within the DST client module 34, the outbound DST processing section 80receives the data 92 and the task(s) 94. The outbound DST processingsection 80 processes the data 92 to produce slice groupings 96. As anexample of such processing, the outbound DST processing section 80partitions the data 92 into a plurality of data partitions. For eachdata partition, the outbound DST processing section 80 dispersed storage(DS) error encodes the data partition to produce encoded data slices andgroups the encoded data slices into a slice grouping 96. In addition,the outbound DST processing section 80 partitions the task 94 intopartial tasks 98, where the number of partial tasks 98 may correspond tothe number of slice groupings 96.

The outbound DST processing section 80 then sends, via the network 24,the slice groupings 96 and the partial tasks 98 to the DST executionunits 1-n of the DSTN module 22 of FIG. 1. For example, the outbound DSTprocessing section 80 sends slice group 1 and partial task 1 to DSTexecution unit 1. As another example, the outbound DST processingsection 80 sends slice group #n and partial task #n to DST executionunit #n.

Each DST execution unit performs its partial task 98 upon its slicegroup 96 to produce partial results 102. For example, DST execution unit#1 performs partial task #1 on slice group #1 to produce a partialresult #1, for results. As a more specific example, slice group #1corresponds to a data partition of a series of digital books and thepartial task #1 corresponds to searching for specific phrases, recordingwhere the phrase is found, and establishing a phrase count. In this morespecific example, the partial result #1 includes information as to wherethe phrase was found and includes the phrase count.

Upon completion of generating their respective partial results 102, theDST execution units send, via the network 24, their partial results 102to the inbound DST processing section 82 of the DST client module 34.The inbound DST processing section 82 processes the received partialresults 102 to produce a result 104. Continuing with the specificexample of the preceding paragraph, the inbound DST processing section82 combines the phrase count from each of the DST execution units 36 toproduce a total phrase count. In addition, the inbound DST processingsection 82 combines the ‘where the phrase was found’ information fromeach of the DST execution units 36 within their respective datapartitions to produce ‘where the phrase was found’ information for theseries of digital books.

In another example of operation, the DST client module 34 requestsretrieval of stored data within the memory of the DST execution units 36(e.g., memory of the DSTN module). In this example, the task 94 isretrieve data stored in the memory of the DSTN module. Accordingly, theoutbound DST processing section 80 converts the task 94 into a pluralityof partial tasks 98 and sends the partial tasks 98 to the respective DSTexecution units 1-n.

In response to the partial task 98 of retrieving stored data, a DSTexecution unit 36 identifies the corresponding encoded data slices 100and retrieves them. For example, DST execution unit #1 receives partialtask #1 and retrieves, in response thereto, retrieved slices #1. The DSTexecution units 36 send their respective retrieved slices 100 to theinbound DST processing section 82 via the network 24.

The inbound DST processing section 82 converts the retrieved slices 100into data 92. For example, the inbound DST processing section 82de-groups the retrieved slices 100 to produce encoded slices per datapartition. The inbound DST processing section 82 then DS error decodesthe encoded slices per data partition to produce data partitions. Theinbound DST processing section 82 de-partitions the data partitions torecapture the data 92.

FIG. 4 is a schematic block diagram of an embodiment of an outbounddistributed storage and/or task (DST) processing section 80 of a DSTclient module 34 FIG. 1 coupled to a DSTN module 22 of a FIG. 1 (e.g., aplurality of n DST execution units 36) via a network 24. The outboundDST processing section 80 includes a data partitioning module 110, adispersed storage (DS) error encoding module 112, a grouping selectormodule 114, a control module 116, and a distributed task control module118.

In an example of operation, the data partitioning module 110 partitionsdata 92 into a plurality of data partitions 120. The number ofpartitions and the size of the partitions may be selected by the controlmodule 116 via control 160 based on the data 92 (e.g., its size, itscontent, etc.), a corresponding task 94 to be performed (e.g., simple,complex, single step, multiple steps, etc.), DS encoding parameters(e.g., pillar width, decode threshold, write threshold, segment securityparameters, slice security parameters, etc.), capabilities of the DSTexecution units 36 (e.g., processing resources, availability ofprocessing recourses, etc.), and/or as may be inputted by a user, systemadministrator, or other operator (human or automated). For example, thedata partitioning module 110 partitions the data 92 (e.g., 100Terabytes) into 100,000 data segments, each being 1 Gigabyte in size.Alternatively, the data partitioning module 110 partitions the data 92into a plurality of data segments, where some of data segments are of adifferent size, are of the same size, or a combination thereof.

The DS error encoding module 112 receives the data partitions 120 in aserial manner, a parallel manner, and/or a combination thereof. For eachdata partition 120, the DS error encoding module 112 DS error encodesthe data partition 120 in accordance with control information 160 fromthe control module 116 to produce encoded data slices 122. The DS errorencoding includes segmenting the data partition into data segments,segment security processing (e.g., encryption, compression,watermarking, integrity check (e.g., CRC), etc.), error encoding,slicing, and/or per slice security processing (e.g., encryption,compression, watermarking, integrity check (e.g., CRC), etc.). Thecontrol information 160 indicates which steps of the DS error encodingare active for a given data partition and, for active steps, indicatesthe parameters for the step. For example, the control information 160indicates that the error encoding is active and includes error encodingparameters (e.g., pillar width, decode threshold, write threshold, readthreshold, type of error encoding, etc.).

The grouping selector module 114 groups the encoded slices 122 of a datapartition into a set of slice groupings 96. The number of slicegroupings corresponds to the number of DST execution units 36 identifiedfor a particular task 94. For example, if five DST execution units 36are identified for the particular task 94, the grouping selector modulegroups the encoded slices 122 of a data partition into five slicegroupings 96. The grouping selector module 114 outputs the slicegroupings 96 to the corresponding DST execution units 36 via the network24.

The distributed task control module 118 receives the task 94 andconverts the task 94 into a set of partial tasks 98. For example, thedistributed task control module 118 receives a task to find where in thedata (e.g., a series of books) a phrase occurs and a total count of thephrase usage in the data. In this example, the distributed task controlmodule 118 replicates the task 94 for each DST execution unit 36 toproduce the partial tasks 98. In another example, the distributed taskcontrol module 118 receives a task to find where in the data a firstphrase occurs, where in the data a second phrase occurs, and a totalcount for each phrase usage in the data. In this example, thedistributed task control module 118 generates a first set of partialtasks 98 for finding and counting the first phrase and a second set ofpartial tasks for finding and counting the second phrase. Thedistributed task control module 118 sends respective first and/or secondpartial tasks 98 to each DST execution unit 36.

FIG. 5 is a logic diagram of an example of a method for outbounddistributed storage and task (DST) processing that begins at step 126where a DST client module receives data and one or more correspondingtasks. The method continues at step 128 where the DST client moduledetermines a number of DST units to support the task for one or moredata partitions. For example, the DST client module may determine thenumber of DST units to support the task based on the size of the data,the requested task, the content of the data, a predetermined number(e.g., user indicated, system administrator determined, etc.), availableDST units, capability of the DST units, and/or any other factorregarding distributed task processing of the data. The DST client modulemay select the same DST units for each data partition, may selectdifferent DST units for the data partitions, or a combination thereof.

The method continues at step 130 where the DST client module determinesprocessing parameters of the data based on the number of DST unitsselected for distributed task processing. The processing parametersinclude data partitioning information, DS encoding parameters, and/orslice grouping information. The data partitioning information includes anumber of data partitions, size of each data partition, and/ororganization of the data partitions (e.g., number of data blocks in apartition, the size of the data blocks, and arrangement of the datablocks). The DS encoding parameters include segmenting information,segment security information, error encoding information (e.g.,dispersed storage error encoding function parameters including one ormore of pillar width, decode threshold, write threshold, read threshold,generator matrix), slicing information, and/or per slice securityinformation. The slice grouping information includes informationregarding how to arrange the encoded data slices into groups for theselected DST units. As a specific example, if the DST client moduledetermines that five DST units are needed to support the task, then itdetermines that the error encoding parameters include a pillar width offive and a decode threshold of three.

The method continues at step 132 where the DST client module determinestask partitioning information (e.g., how to partition the tasks) basedon the selected DST units and data processing parameters. The dataprocessing parameters include the processing parameters and DST unitcapability information. The DST unit capability information includes thenumber of DT (distributed task) execution units, execution capabilitiesof each DT execution unit (e.g., MIPS capabilities, processing resources(e.g., quantity and capability of microprocessors, CPUs, digital signalprocessors, co-processor, microcontrollers, arithmetic logic circuitry,and/or any other analog and/or digital processing circuitry),availability of the processing resources, memory information (e.g.,type, size, availability, etc.)), and/or any information germane toexecuting one or more tasks.

The method continues at step 134 where the DST client module processesthe data in accordance with the processing parameters to produce slicegroupings. The method continues at step 136 where the DST client modulepartitions the task based on the task partitioning information toproduce a set of partial tasks. The method continues at step 138 wherethe DST client module sends the slice groupings and the correspondingpartial tasks to respective DST units.

FIG. 6 is a schematic block diagram of an embodiment of the dispersedstorage (DS) error encoding module 112 of an outbound distributedstorage and task (DST) processing section. The DS error encoding module112 includes a segment processing module 142, a segment securityprocessing module 144, an error encoding module 146, a slicing module148, and a per slice security processing module 150. Each of thesemodules is coupled to a control module 116 to receive controlinformation 160 therefrom.

In an example of operation, the segment processing module 142 receives adata partition 120 from a data partitioning module and receivessegmenting information as the control information 160 from the controlmodule 116. The segmenting information indicates how the segmentprocessing module 142 is to segment the data partition 120. For example,the segmenting information indicates how many rows to segment the databased on a decode threshold of an error encoding scheme, indicates howmany columns to segment the data into based on a number and size of datablocks within the data partition 120, and indicates how many columns toinclude in a data segment 152. The segment processing module 142segments the data 120 into data segments 152 in accordance with thesegmenting information.

The segment security processing module 144, when enabled by the controlmodule 116, secures the data segments 152 based on segment securityinformation received as control information 160 from the control module116. The segment security information includes data compression,encryption, watermarking, integrity check (e.g., cyclic redundancy check(CRC), etc.), and/or any other type of digital security. For example,when the segment security processing module 144 is enabled, it maycompress a data segment 152, encrypt the compressed data segment, andgenerate a CRC value for the encrypted data segment to produce a securedata segment 154. When the segment security processing module 144 is notenabled, it passes the data segments 152 to the error encoding module146 or is bypassed such that the data segments 152 are provided to theerror encoding module 146.

The error encoding module 146 encodes the secure data segments 154 inaccordance with error correction encoding parameters received as controlinformation 160 from the control module 116. The error correctionencoding parameters (e.g., also referred to as dispersed storage errorcoding parameters) include identifying an error correction encodingscheme (e.g., forward error correction algorithm, a Reed-Solomon basedalgorithm, an online coding algorithm, an information dispersalalgorithm, etc.), a pillar width, a decode threshold, a read threshold,a write threshold, etc. For example, the error correction encodingparameters identify a specific error correction encoding scheme,specifies a pillar width of five, and specifies a decode threshold ofthree. From these parameters, the error encoding module 146 encodes adata segment 154 to produce an encoded data segment 156.

The slicing module 148 slices the encoded data segment 156 in accordancewith the pillar width of the error correction encoding parametersreceived as control information 160. For example, if the pillar width isfive, the slicing module 148 slices an encoded data segment 156 into aset of five encoded data slices. As such, for a plurality of encodeddata segments 156 for a given data partition, the slicing module outputsa plurality of sets of encoded data slices 158.

The per slice security processing module 150, when enabled by thecontrol module 116, secures each encoded data slice 158 based on slicesecurity information received as control information 160 from thecontrol module 116. The slice security information includes datacompression, encryption, watermarking, integrity check (e.g., CRC,etc.), and/or any other type of digital security. For example, when theper slice security processing module 150 is enabled, it compresses anencoded data slice 158, encrypts the compressed encoded data slice, andgenerates a CRC value for the encrypted encoded data slice to produce asecure encoded data slice 122. When the per slice security processingmodule 150 is not enabled, it passes the encoded data slices 158 or isbypassed such that the encoded data slices 158 are the output of the DSerror encoding module 112. Note that the control module 116 may beomitted and each module stores its own parameters.

FIG. 7 is a diagram of an example of a segment processing of a dispersedstorage (DS) error encoding module. In this example, a segmentprocessing module 142 receives a data partition 120 that includes 45data blocks (e.g., dl-d45), receives segmenting information (i.e.,control information 160) from a control module, and segments the datapartition 120 in accordance with the control information 160 to producedata segments 152. Each data block may be of the same size as other datablocks or of a different size. In addition, the size of each data blockmay be a few bytes to megabytes of data. As previously mentioned, thesegmenting information indicates how many rows to segment the datapartition into, indicates how many columns to segment the data partitioninto, and indicates how many columns to include in a data segment.

In this example, the decode threshold of the error encoding scheme isthree; as such the number of rows to divide the data partition into isthree. The number of columns for each row is set to 15, which is basedon the number and size of data blocks. The data blocks of the datapartition are arranged in rows and columns in a sequential order (i.e.,the first row includes the first 15 data blocks; the second row includesthe second 15 data blocks; and the third row includes the last 15 datablocks).

With the data blocks arranged into the desired sequential order, theyare divided into data segments based on the segmenting information. Inthis example, the data partition is divided into 8 data segments; thefirst 7 include 2 columns of three rows and the last includes 1 columnof three rows. Note that the first row of the 8 data segments is insequential order of the first 15 data blocks; the second row of the 8data segments in sequential order of the second 15 data blocks; and thethird row of the 8 data segments in sequential order of the last 15 datablocks. Note that the number of data blocks, the grouping of the datablocks into segments, and size of the data blocks may vary toaccommodate the desired distributed task processing function.

FIG. 8 is a diagram of an example of error encoding and slicingprocessing of the dispersed error encoding processing the data segmentsof FIG. 7. In this example, data segment 1 includes 3 rows with each rowbeing treated as one word for encoding. As such, data segment 1 includesthree words for encoding: word 1 including data blocks d1 and d2, word 2including data blocks d16 and d17, and word 3 including data blocks d31and d32. Each of data segments 2-7 includes three words where each wordincludes two data blocks. Data segment 8 includes three words where eachword includes a single data block (e.g., d15, d30, and d45).

In operation, an error encoding module 146 and a slicing module 148convert each data segment into a set of encoded data slices inaccordance with error correction encoding parameters as controlinformation 160. More specifically, when the error correction encodingparameters indicate a unity matrix Reed-Solomon based encodingalgorithm, 5 pillars, and decode threshold of 3, the first three encodeddata slices of the set of encoded data slices for a data segment aresubstantially similar to the corresponding word of the data segment. Forinstance, when the unity matrix Reed-Solomon based encoding algorithm isapplied to data segment 1, the content of the first encoded data slice(DS1_d1&2) of the first set of encoded data slices (e.g., correspondingto data segment 1) is substantially similar to content of the first word(e.g., d1 & d2); the content of the second encoded data slice(DS1_d16&17) of the first set of encoded data slices is substantiallysimilar to content of the second word (e.g., d16 & d17); and the contentof the third encoded data slice (DS1_d31&32) of the first set of encodeddata slices is substantially similar to content of the third word (e.g.,d31 & d32).

The content of the fourth and fifth encoded data slices (e.g., ES1_1 andES1_2) of the first set of encoded data slices include error correctiondata based on the first-third words of the first data segment. With suchan encoding and slicing scheme, retrieving any three of the five encodeddata slices allows the data segment to be accurately reconstructed.

The encoding and slicing of data segments 2-7 yield sets of encoded dataslices similar to the set of encoded data slices of data segment 1. Forinstance, the content of the first encoded data slice (DS2_d3&4) of thesecond set of encoded data slices (e.g., corresponding to data segment2) is substantially similar to content of the first word (e.g., d3 &d4); the content of the second encoded data slice (DS2_d18&19) of thesecond set of encoded data slices is substantially similar to content ofthe second word (e.g., d18 & d19); and the content of the third encodeddata slice (DS2_d33&34) of the second set of encoded data slices issubstantially similar to content of the third word (e.g., d33 & d34).The content of the fourth and fifth encoded data slices (e.g., ES1_1 andES1_2) of the second set of encoded data slices includes errorcorrection data based on the first-third words of the second datasegment.

FIG. 9 is a diagram of an example of grouping selection processing of anoutbound distributed storage and task (DST) processing in accordancewith group selection information as control information 160 from acontrol module. Encoded slices for data partition 122 are grouped inaccordance with the control information 160 to produce slice groupings96. In this example, a grouping selector module 114 organizes theencoded data slices into five slice groupings (e.g., one for each DSTexecution unit of a distributed storage and task network (DSTN) module).As a specific example, the grouping selector module 114 creates a firstslice grouping for a DST execution unit #1, which includes first encodedslices of each of the sets of encoded slices. As such, the first DSTexecution unit receives encoded data slices corresponding to data blocks1-15 (e.g., encoded data slices of contiguous data).

The grouping selector module 114 also creates a second slice groupingfor a DST execution unit #2, which includes second encoded slices ofeach of the sets of encoded slices. As such, the second DST executionunit receives encoded data slices corresponding to data blocks 16-30.The grouping selector module 114 further creates a third slice groupingfor DST execution unit #3, which includes third encoded slices of eachof the sets of encoded slices. As such, the third DST execution unitreceives encoded data slices corresponding to data blocks 31-45.

The grouping selector module 114 creates a fourth slice grouping for DSTexecution unit #4, which includes fourth encoded slices of each of thesets of encoded slices. As such, the fourth DST execution unit receivesencoded data slices corresponding to first error encoding information(e.g., encoded data slices of error coding (EC) data). The groupingselector module 114 further creates a fifth slice grouping for DSTexecution unit #5, which includes fifth encoded slices of each of thesets of encoded slices. As such, the fifth DST execution unit receivesencoded data slices corresponding to second error encoding information.

FIG. 10 is a diagram of an example of converting data 92 into slicegroups that expands on the preceding figures. As shown, the data 92 ispartitioned in accordance with a partitioning function 164 into aplurality of data partitions (1-x, where x is an integer greater than4). Each data partition (or chunkset of data) is encoded and groupedinto slice groupings as previously discussed by an encoding and groupingfunction 166. For a given data partition, the slice groupings are sentto distributed storage and task (DST) execution units. From datapartition to data partition, the ordering of the slice groupings to theDST execution units may vary.

For example, the slice groupings of data partition #1 is sent to the DSTexecution units such that the first DST execution receives first encodeddata slices of each of the sets of encoded data slices, whichcorresponds to a first continuous data chunk of the first data partition(e.g., refer to FIG. 9), a second DST execution receives second encodeddata slices of each of the sets of encoded data slices, whichcorresponds to a second continuous data chunk of the first datapartition, etc.

For the second data partition, the slice groupings may be sent to theDST execution units in a different order than it was done for the firstdata partition. For instance, the first slice grouping of the seconddata partition (e.g., slice group 2_1) is sent to the second DSTexecution unit; the second slice grouping of the second data partition(e.g., slice group 2_2) is sent to the third DST execution unit; thethird slice grouping of the second data partition (e.g., slice group2_3) is sent to the fourth DST execution unit; the fourth slice groupingof the second data partition (e.g., slice group 2_4, which includesfirst error coding information) is sent to the fifth DST execution unit;and the fifth slice grouping of the second data partition (e.g., slicegroup 2_5, which includes second error coding information) is sent tothe first DST execution unit.

The pattern of sending the slice groupings to the set of DST executionunits may vary in a predicted pattern, a random pattern, and/or acombination thereof from data partition to data partition. In addition,from data partition to data partition, the set of DST execution unitsmay change. For example, for the first data partition, DST executionunits 1-5 may be used; for the second data partition, DST executionunits 6-10 may be used; for the third data partition, DST executionunits 3-7 may be used; etc. As is also shown, the task is divided intopartial tasks that are sent to the DST execution units in conjunctionwith the slice groupings of the data partitions.

FIG. 11 is a schematic block diagram of an embodiment of a DST(distributed storage and/or task) execution unit that includes aninterface 169, a controller 86, memory 88, one or more DT (distributedtask) execution modules 90, and a DST client module 34. The memory 88 isof sufficient size to store a significant number of encoded data slices(e.g., thousands of slices to hundreds-of-millions of slices) and mayinclude one or more hard drives and/or one or more solid-state memorydevices (e.g., flash memory, DRAM, etc.).

In an example of storing a slice group, the DST execution modulereceives a slice grouping 96 (e.g., slice group #1) via interface 169.The slice grouping 96 includes, per partition, encoded data slices ofcontiguous data or encoded data slices of error coding (EC) data. Forslice group #1, the DST execution module receives encoded data slices ofcontiguous data for partitions #1 and #x (and potentially others between3 and x) and receives encoded data slices of EC data for partitions #2and #3 (and potentially others between 3 and x). Examples of encodeddata slices of contiguous data and encoded data slices of error coding(EC) data are discussed with reference to FIG. 9. The memory 88 storesthe encoded data slices of slice groupings 96 in accordance with memorycontrol information 174 it receives from the controller 86.

The controller 86 (e.g., a processing module, a CPU, etc.) generates thememory control information 174 based on a partial task(s) 98 anddistributed computing information (e.g., user information (e.g., userID, distributed computing permissions, data access permission, etc.),vault information (e.g., virtual memory assigned to user, user group,temporary storage for task processing, etc.), task validationinformation, etc.). For example, the controller 86 interprets thepartial task(s) 98 in light of the distributed computing information todetermine whether a requestor is authorized to perform the task 98, isauthorized to access the data, and/or is authorized to perform the taskon this particular data. When the requestor is authorized, thecontroller 86 determines, based on the task 98 and/or another input,whether the encoded data slices of the slice grouping 96 are to betemporarily stored or permanently stored. Based on the foregoing, thecontroller 86 generates the memory control information 174 to write theencoded data slices of the slice grouping 96 into the memory 88 and toindicate whether the slice grouping 96 is permanently stored ortemporarily stored.

With the slice grouping 96 stored in the memory 88, the controller 86facilitates execution of the partial task(s) 98. In an example, thecontroller 86 interprets the partial task 98 in light of thecapabilities of the DT execution module(s) 90. The capabilities includeone or more of MIPS capabilities, processing resources (e.g., quantityand capability of microprocessors, CPUs, digital signal processors,co-processor, microcontrollers, arithmetic logic circuitry, and/or anyother analog and/or digital processing circuitry), availability of theprocessing resources, etc. If the controller 86 determines that the DTexecution module(s) 90 have sufficient capabilities, it generates taskcontrol information 176.

The task control information 176 may be a generic instruction (e.g.,perform the task on the stored slice grouping) or a series ofoperational codes. In the former instance, the DT execution module 90includes a co-processor function specifically configured (fixed orprogrammed) to perform the desired task 98. In the latter instance, theDT execution module 90 includes a general processor topology where thecontroller stores an algorithm corresponding to the particular task 98.In this instance, the controller 86 provides the operational codes(e.g., assembly language, source code of a programming language, objectcode, etc.) of the algorithm to the DT execution module 90 forexecution.

Depending on the nature of the task 98, the DT execution module 90 maygenerate intermediate partial results 102 that are stored in the memory88 or in a cache memory (not shown) within the DT execution module 90.In either case, when the DT execution module 90 completes execution ofthe partial task 98, it outputs one or more partial results 102. Thepartial results 102 may also be stored in memory 88.

If, when the controller 86 is interpreting whether capabilities of theDT execution module(s) 90 can support the partial task 98, thecontroller 86 determines that the DT execution module(s) 90 cannotadequately support the task 98 (e.g., does not have the right resources,does not have sufficient available resources, available resources wouldbe too slow, etc.), it then determines whether the partial task 98should be fully offloaded or partially offloaded.

If the controller 86 determines that the partial task 98 should be fullyoffloaded, it generates DST control information 178 and provides it tothe DST client module 34. The DST control information 178 includes thepartial task 98, memory storage information regarding the slice grouping96, and distribution instructions. The distribution instructionsinstruct the DST client module 34 to divide the partial task 98 intosub-partial tasks 172, to divide the slice grouping 96 into sub-slicegroupings 170, and identify other DST execution units. The DST clientmodule 34 functions in a similar manner as the DST client module 34 ofFIGS. 3-10 to produce the sub-partial tasks 172 and the sub-slicegroupings 170 in accordance with the distribution instructions.

The DST client module 34 receives DST feedback 168 (e.g., sub-partialresults), via the interface 169, from the DST execution units to whichthe task was offloaded. The DST client module 34 provides thesub-partial results to the DST execution unit, which processes thesub-partial results to produce the partial result(s) 102.

If the controller 86 determines that the partial task 98 should bepartially offloaded, it determines what portion of the task 98 and/orslice grouping 96 should be processed locally and what should beoffloaded. For the portion that is being locally processed, thecontroller 86 generates task control information 176 as previouslydiscussed. For the portion that is being offloaded, the controller 86generates DST control information 178 as previously discussed.

When the DST client module 34 receives DST feedback 168 (e.g.,sub-partial results) from the DST executions units to which a portion ofthe task was offloaded, it provides the sub-partial results to the DTexecution module 90. The DT execution module 90 processes thesub-partial results with the sub-partial results it created to producethe partial result(s) 102.

The memory 88 may be further utilized to retrieve one or more of storedslices 100, stored results 104, partial results 102 when the DTexecution module 90 stores partial results 102 and/or results 104 in thememory 88. For example, when the partial task 98 includes a retrievalrequest, the controller 86 outputs the memory control 174 to the memory88 to facilitate retrieval of slices 100 and/or results 104.

FIG. 12 is a schematic block diagram of an example of operation of adistributed storage and task (DST) execution unit storing encoded dataslices and executing a task thereon. To store the encoded data slices ofa partition 1 of slice grouping 1, a controller 86 generates writecommands as memory control information 174 such that the encoded slicesare stored in desired locations (e.g., permanent or temporary) withinmemory 88.

Once the encoded slices are stored, the controller 86 provides taskcontrol information 176 to a distributed task (DT) execution module 90.As a first step of executing the task in accordance with the taskcontrol information 176, the DT execution module 90 retrieves theencoded slices from memory 88. The DT execution module 90 thenreconstructs contiguous data blocks of a data partition. As shown forthis example, reconstructed contiguous data blocks of data partition 1include data blocks 1-15 (e.g., d1-d15).

With the contiguous data blocks reconstructed, the DT execution module90 performs the task on the reconstructed contiguous data blocks. Forexample, the task may be to search the reconstructed contiguous datablocks for a particular word or phrase, identify where in thereconstructed contiguous data blocks the particular word or phraseoccurred, and/or count the occurrences of the particular word or phraseon the reconstructed contiguous data blocks. The DST execution unitcontinues in a similar manner for the encoded data slices of otherpartitions in slice grouping 1. Note that with using the unity matrixerror encoding scheme previously discussed, if the encoded data slicesof contiguous data are uncorrupted, the decoding of them is a relativelystraightforward process of extracting the data.

If, however, an encoded data slice of contiguous data is corrupted (ormissing), it can be rebuilt by accessing other DST execution units thatare storing the other encoded data slices of the set of encoded dataslices of the corrupted encoded data slice. In this instance, the DSTexecution unit having the corrupted encoded data slices retrieves atleast three encoded data slices (of contiguous data and of error codingdata) in the set from the other DST execution units (recall for thisexample, the pillar width is 5 and the decode threshold is 3). The DSTexecution unit decodes the retrieved data slices using the DS errorencoding parameters to recapture the corresponding data segment. The DSTexecution unit then re-encodes the data segment using the DS errorencoding parameters to rebuild the corrupted encoded data slice. Oncethe encoded data slice is rebuilt, the DST execution unit functions aspreviously described.

FIG. 13 is a schematic block diagram of an embodiment of an inbounddistributed storage and/or task (DST) processing section 82 of a DSTclient module coupled to DST execution units of a distributed storageand task network (DSTN) module via a network 24. The inbound DSTprocessing section 82 includes a de-grouping module 180, a DS (dispersedstorage) error decoding module 182, a data de-partitioning module 184, acontrol module 186, and a distributed task control module 188. Note thatthe control module 186 and/or the distributed task control module 188may be separate modules from corresponding ones of outbound DSTprocessing section or may be the same modules.

In an example of operation, the DST execution units have completedexecution of corresponding partial tasks on the corresponding slicegroupings to produce partial results 102. The inbound DST processingsection 82 receives the partial results 102 via the distributed taskcontrol module 188. The inbound DST processing section 82 then processesthe partial results 102 to produce a final result, or results 104. Forexample, if the task was to find a specific word or phrase within data,the partial results 102 indicate where in each of the prescribedportions of the data the corresponding DST execution units found thespecific word or phrase. The distributed task control module 188combines the individual partial results 102 for the correspondingportions of the data into a final result 104 for the data as a whole.

In another example of operation, the inbound DST processing section 82is retrieving stored data from the DST execution units (i.e., the DSTNmodule). In this example, the DST execution units output encoded dataslices 100 corresponding to the data retrieval requests. The de-groupingmodule 180 receives retrieved slices 100 and de-groups them to produceencoded data slices per data partition 122. The DS error decoding module182 decodes, in accordance with DS error encoding parameters, theencoded data slices per data partition 122 to produce data partitions120.

The data de-partitioning module 184 combines the data partitions 120into the data 92. The control module 186 controls the conversion ofretrieved slices 100 into the data 92 using control signals 190 to eachof the modules. For instance, the control module 186 providesde-grouping information to the de-grouping module 180, provides the DSerror encoding parameters to the DS error decoding module 182, andprovides de-partitioning information to the data de-partitioning module184.

FIG. 14 is a logic diagram of an example of a method that is executableby distributed storage and task (DST) client module regarding inboundDST processing. The method begins at step 194 where the DST clientmodule receives partial results. The method continues at step 196 wherethe DST client module retrieves the task corresponding to the partialresults. For example, the partial results include header informationthat identifies the requesting entity, which correlates to the requestedtask.

The method continues at step 198 where the DST client module determinesresult processing information based on the task. For example, if thetask were to identify a particular word or phrase within the data, theresult processing information would indicate to aggregate the partialresults for the corresponding portions of the data to produce the finalresult. As another example, if the task were to count the occurrences ofa particular word or phrase within the data, results of processing theinformation would indicate to add the partial results to produce thefinal results. The method continues at step 200 where the DST clientmodule processes the partial results in accordance with the resultprocessing information to produce the final result or results.

FIG. 15 is a diagram of an example of de-grouping selection processingof an inbound distributed storage and task (DST) processing section of aDST client module. In general, this is an inverse process of thegrouping module of the outbound DST processing section of FIG. 9.Accordingly, for each data partition (e.g., partition #1), thede-grouping module retrieves the corresponding slice grouping from theDST execution units (EU) (e.g., DST 1-5).

As shown, DST execution unit #1 provides a first slice grouping, whichincludes the first encoded slices of each of the sets of encoded slices(e.g., encoded data slices of contiguous data of data blocks 1-15); DSTexecution unit #2 provides a second slice grouping, which includes thesecond encoded slices of each of the sets of encoded slices (e.g.,encoded data slices of contiguous data of data blocks 16-30); DSTexecution unit #3 provides a third slice grouping, which includes thethird encoded slices of each of the sets of encoded slices (e.g.,encoded data slices of contiguous data of data blocks 31-45); DSTexecution unit #4 provides a fourth slice grouping, which includes thefourth encoded slices of each of the sets of encoded slices (e.g., firstencoded data slices of error coding (EC) data); and DST execution unit#5 provides a fifth slice grouping, which includes the fifth encodedslices of each of the sets of encoded slices (e.g., first encoded dataslices of error coding (EC) data).

The de-grouping module de-groups the slice groupings (e.g., receivedslices 100) using a de-grouping selector 180 controlled by a controlsignal 190 as shown in the example to produce a plurality of sets ofencoded data slices (e.g., retrieved slices for a partition into sets ofslices 122). Each set corresponding to a data segment of the datapartition.

FIG. 16 is a schematic block diagram of an embodiment of a dispersedstorage (DS) error decoding module 182 of an inbound distributed storageand task (DST) processing section. The DS error decoding module 182includes an inverse per slice security processing module 202, ade-slicing module 204, an error decoding module 206, an inverse segmentsecurity module 208, a de-segmenting processing module 210, and acontrol module 186.

In an example of operation, the inverse per slice security processingmodule 202, when enabled by the control module 186, unsecures eachencoded data slice 122 based on slice de-security information receivedas control information 190 (e.g., the compliment of the slice securityinformation discussed with reference to FIG. 6) received from thecontrol module 186. The slice security information includes datadecompression, decryption, de-watermarking, integrity check (e.g., CRCverification, etc.), and/or any other type of digital security. Forexample, when the inverse per slice security processing module 202 isenabled, it verifies integrity information (e.g., a CRC value) of eachencoded data slice 122, it decrypts each verified encoded data slice,and decompresses each decrypted encoded data slice to produce sliceencoded data 158. When the inverse per slice security processing module202 is not enabled, it passes the encoded data slices 122 as the slicedencoded data 158 or is bypassed such that the retrieved encoded dataslices 122 are provided as the sliced encoded data 158.

The de-slicing module 204 de-slices the sliced encoded data 158 intoencoded data segments 156 in accordance with a pillar width of the errorcorrection encoding parameters received as control information 190 fromthe control module 186. For example, if the pillar width is five, thede-slicing module 204 de-slices a set of five encoded data slices intoan encoded data segment 156. The error decoding module 206 decodes theencoded data segments 156 in accordance with error correction decodingparameters received as control information 190 from the control module186 to produce secure data segments 154. The error correction decodingparameters include identifying an error correction encoding scheme(e.g., forward error correction algorithm, a Reed-Solomon basedalgorithm, an information dispersal algorithm, etc.), a pillar width, adecode threshold, a read threshold, a write threshold, etc. For example,the error correction decoding parameters identify a specific errorcorrection encoding scheme, specify a pillar width of five, and specifya decode threshold of three.

The inverse segment security processing module 208, when enabled by thecontrol module 186, unsecures the secured data segments 154 based onsegment security information received as control information 190 fromthe control module 186. The segment security information includes datadecompression, decryption, de-watermarking, integrity check (e.g., CRC,etc.) verification, and/or any other type of digital security. Forexample, when the inverse segment security processing module 208 isenabled, it verifies integrity information (e.g., a CRC value) of eachsecure data segment 154, it decrypts each verified secured data segment,and decompresses each decrypted secure data segment to produce a datasegment 152. When the inverse segment security processing module 208 isnot enabled, it passes the decoded data segment 154 as the data segment152 or is bypassed.

The de-segment processing module 210 receives the data segments 152 andreceives de-segmenting information as control information 190 from thecontrol module 186. The de-segmenting information indicates how thede-segment processing module 210 is to de-segment the data segments 152into a data partition 120. For example, the de-segmenting informationindicates how the rows and columns of data segments are to be rearrangedto yield the data partition 120.

FIG. 17 is a diagram of an example of de-slicing and error decodingprocessing of a dispersed error decoding module. A de-slicing module 204receives at least a decode threshold number of encoded data slices 158for each data segment in accordance with control information 190 andprovides encoded data 156. In this example, a decode threshold is three.As such, each set of encoded data slices 158 is shown to have threeencoded data slices per data segment. The de-slicing module 204 mayreceive three encoded data slices per data segment because an associateddistributed storage and task (DST) client module requested retrievingonly three encoded data slices per segment or selected three of theretrieved encoded data slices per data segment. As shown, which is basedon the unity matrix encoding previously discussed with reference to FIG.8, an encoded data slice may be a data-based encoded data slice (e.g.,DS1_d1&d2) or an error code based encoded data slice (e.g., ES3_1).

An error decoding module 206 decodes the encoded data 156 of each datasegment in accordance with the error correction decoding parameters ofcontrol information 190 to produce secured segments 154. In thisexample, data segment 1 includes 3 rows with each row being treated asone word for encoding. As such, data segment 1 includes three words:word 1 including data blocks d1 and d2, word 2 including data blocks d16and d17, and word 3 including data blocks d31 and d32. Each of datasegments 2-7 includes three words where each word includes two datablocks. Data segment 8 includes three words where each word includes asingle data block (e.g., d15, d30, and d45).

FIG. 18 is a diagram of an example of de-segment processing of aninbound distributed storage and task (DST) processing. In this example,a de-segment processing module 210 receives data segments 152 (e.g.,1-8) and rearranges the data blocks of the data segments into rows andcolumns in accordance with de-segmenting information of controlinformation 190 to produce a data partition 120. Note that the number ofrows is based on the decode threshold (e.g., 3 in this specific example)and the number of columns is based on the number and size of the datablocks.

The de-segmenting module 210 converts the rows and columns of datablocks into the data partition 120. Note that each data block may be ofthe same size as other data blocks or of a different size. In addition,the size of each data block may be a few bytes to megabytes of data.

FIG. 19 is a diagram of an example of converting slice groups into data92 within an inbound distributed storage and task (DST) processingsection. As shown, the data 92 is reconstructed from a plurality of datapartitions (1-x, where x is an integer greater than 4). Each datapartition (or chunk set of data) is decoded and re-grouped using ade-grouping and decoding function 212 and a de-partition function 214from slice groupings as previously discussed. For a given datapartition, the slice groupings (e.g., at least a decode threshold perdata segment of encoded data slices) are received from DST executionunits. From data partition to data partition, the ordering of the slicegroupings received from the DST execution units may vary as discussedwith reference to FIG. 10.

FIG. 20 is a diagram of an example of a distributed storage and/orretrieval within the distributed computing system. The distributedcomputing system includes a plurality of distributed storage and/or task(DST) processing client modules 34 (one shown) coupled to a distributedstorage and/or task processing network (DSTN) module, or multiple DSTNmodules, via a network 24. The DST client module 34 includes an outboundDST processing section 80 and an inbound DST processing section 82. TheDSTN module includes a plurality of DST execution units. Each DSTexecution unit includes a controller 86, memory 88, one or moredistributed task (DT) execution modules 90, and a DST client module 34.

In an example of data storage, the DST client module 34 has data 92 thatit desires to store in the DSTN module. The data 92 may be a file (e.g.,video, audio, text, graphics, etc.), a data object, a data block, anupdate to a file, an update to a data block, etc. In this instance, theoutbound DST processing module 80 converts the data 92 into encoded dataslices 216 as will be further described with reference to FIGS. 21-23.The outbound DST processing module 80 sends, via the network 24, to theDST execution units for storage as further described with reference toFIG. 24.

In an example of data retrieval, the DST client module 34 issues aretrieve request to the DST execution units for the desired data 92. Theretrieve request may address each DST executions units storing encodeddata slices of the desired data, address a decode threshold number ofDST execution units, address a read threshold number of DST executionunits, or address some other number of DST execution units. In responseto the request, each addressed DST execution unit retrieves its encodeddata slices 100 of the desired data and sends them to the inbound DSTprocessing section 82, via the network 24.

When, for each data segment, the inbound DST processing section 82receives at least a decode threshold number of encoded data slices 100,it converts the encoded data slices 100 into a data segment. The inboundDST processing section 82 aggregates the data segments to produce theretrieved data 92.

FIG. 21 is a schematic block diagram of an embodiment of an outbounddistributed storage and/or task (DST) processing section 80 of a DSTclient module coupled to a distributed storage and task network (DSTN)module (e.g., a plurality of DST execution units) via a network 24. Theoutbound DST processing section 80 includes a data partitioning module110, a dispersed storage (DS) error encoding module 112, a groupingselector module 114, a control module 116, and a distributed taskcontrol module 118.

In an example of operation, the data partitioning module 110 isby-passed such that data 92 is provided directly to the DS errorencoding module 112. The control module 116 coordinates the by-passingof the data partitioning module 110 by outputting a bypass 220 messageto the data partitioning module 110.

The DS error encoding module 112 receives the data 92 in a serialmanner, a parallel manner, and/or a combination thereof. The DS errorencoding module 112 DS error encodes the data in accordance with controlinformation 160 from the control module 116 to produce encoded dataslices 218. The DS error encoding includes segmenting the data 92 intodata segments, segment security processing (e.g., encryption,compression, watermarking, integrity check (e.g., CRC, etc.)), errorencoding, slicing, and/or per slice security processing (e.g.,encryption, compression, watermarking, integrity check (e.g., CRC,etc.)). The control information 160 indicates which steps of the DSerror encoding are active for the data 92 and, for active steps,indicates the parameters for the step. For example, the controlinformation 160 indicates that the error encoding is active and includeserror encoding parameters (e.g., pillar width, decode threshold, writethreshold, read threshold, type of error encoding, etc.).

The grouping selector module 114 groups the encoded slices 218 of thedata segments into pillars of slices 216. The number of pillarscorresponds to the pillar width of the DS error encoding parameters. Inthis example, the distributed task control module 118 facilitates thestorage request.

FIG. 22 is a schematic block diagram of an example of a dispersedstorage (DS) error encoding module 112 for the example of FIG. 21. TheDS error encoding module 112 includes a segment processing module 142, asegment security processing module 144, an error encoding module 146, aslicing module 148, and a per slice security processing module 150. Eachof these modules is coupled to a control module 116 to receive controlinformation 160 therefrom.

In an example of operation, the segment processing module 142 receivesdata 92 and receives segmenting information as control information 160from the control module 116. The segmenting information indicates howthe segment processing module is to segment the data. For example, thesegmenting information indicates the size of each data segment. Thesegment processing module 142 segments the data 92 into data segments152 in accordance with the segmenting information.

The segment security processing module 144, when enabled by the controlmodule 116, secures the data segments 152 based on segment securityinformation received as control information 160 from the control module116. The segment security information includes data compression,encryption, watermarking, integrity check (e.g., CRC, etc.), and/or anyother type of digital security. For example, when the segment securityprocessing module 144 is enabled, it compresses a data segment 152,encrypts the compressed data segment, and generates a CRC value for theencrypted data segment to produce a secure data segment. When thesegment security processing module 144 is not enabled, it passes thedata segments 152 to the error encoding module 146 or is bypassed suchthat the data segments 152 are provided to the error encoding module146.

The error encoding module 146 encodes the secure data segments inaccordance with error correction encoding parameters received as controlinformation 160 from the control module 116. The error correctionencoding parameters include identifying an error correction encodingscheme (e.g., forward error correction algorithm, a Reed-Solomon basedalgorithm, an information dispersal algorithm, etc.), a pillar width, adecode threshold, a read threshold, a write threshold, etc. For example,the error correction encoding parameters identify a specific errorcorrection encoding scheme, specifies a pillar width of five, andspecifies a decode threshold of three. From these parameters, the errorencoding module 146 encodes a data segment to produce an encoded datasegment.

The slicing module 148 slices the encoded data segment in accordancewith a pillar width of the error correction encoding parameters. Forexample, if the pillar width is five, the slicing module slices anencoded data segment into a set of five encoded data slices. As such,for a plurality of data segments, the slicing module 148 outputs aplurality of sets of encoded data slices as shown within encoding andslicing function 222 as described.

The per slice security processing module 150, when enabled by thecontrol module 116, secures each encoded data slice based on slicesecurity information received as control information 160 from thecontrol module 116. The slice security information includes datacompression, encryption, watermarking, integrity check (e.g., CRC,etc.), and/or any other type of digital security. For example, when theper slice security processing module 150 is enabled, it may compress anencoded data slice, encrypt the compressed encoded data slice, andgenerate a CRC value for the encrypted encoded data slice to produce asecure encoded data slice tweaking. When the per slice securityprocessing module 150 is not enabled, it passes the encoded data slicesor is bypassed such that the encoded data slices 218 are the output ofthe DS error encoding module 112.

FIG. 23 is a diagram of an example of converting data 92 into pillarslice groups utilizing encoding, slicing and pillar grouping function224 for storage in memory of a distributed storage and task network(DSTN) module. As previously discussed the data 92 is encoded and slicedinto a plurality of sets of encoded data slices; one set per datasegment. The grouping selector module organizes the sets of encoded dataslices into pillars of data slices. In this example, the DS errorencoding parameters include a pillar width of 5 and a decode thresholdof 3. As such, for each data segment, 5 encoded data slices are created.

The grouping selector module takes the first encoded data slice of eachof the sets and forms a first pillar, which may be sent to the first DSTexecution unit. Similarly, the grouping selector module creates thesecond pillar from the second slices of the sets; the third pillar fromthe third slices of the sets; the fourth pillar from the fourth slicesof the sets; and the fifth pillar from the fifth slices of the set.

FIG. 24 is a schematic block diagram of an embodiment of a distributedstorage and/or task (DST) execution unit that includes an interface 169,a controller 86, memory 88, one or more distributed task (DT) executionmodules 90, and a DST client module 34. A computing core 26 may beutilized to implement the one or more DT execution modules 90 and theDST client module 34. The memory 88 is of sufficient size to store asignificant number of encoded data slices (e.g., thousands of slices tohundreds-of-millions of slices) and may include one or more hard drivesand/or one or more solid-state memory devices (e.g., flash memory, DRAM,etc.).

In an example of storing a pillar of slices 216, the DST execution unitreceives, via interface 169, a pillar of slices 216 (e.g., pillar #1slices). The memory 88 stores the encoded data slices 216 of the pillarof slices in accordance with memory control information 174 it receivesfrom the controller 86. The controller 86 (e.g., a processing module, aCPU, etc.) generates the memory control information 174 based ondistributed storage information (e.g., user information (e.g., user ID,distributed storage permissions, data access permission, etc.), vaultinformation (e.g., virtual memory assigned to user, user group, etc.),etc.). Similarly, when retrieving slices, the DST execution unitreceives, via interface 169, a slice retrieval request. The memory 88retrieves the slice in accordance with memory control information 174 itreceives from the controller 86. The memory 88 outputs the slice 100,via the interface 169, to a requesting entity.

FIG. 25 is a schematic block diagram of an example of operation of aninbound distributed storage and/or task (DST) processing section 82 forretrieving dispersed error encoded data 92. The inbound DST processingsection 82 includes a de-grouping module 180, a dispersed storage (DS)error decoding module 182, a data de-partitioning module 184, a controlmodule 186, and a distributed task control module 188. Note that thecontrol module 186 and/or the distributed task control module 188 may beseparate modules from corresponding ones of an outbound DST processingsection or may be the same modules.

In an example of operation, the inbound DST processing section 82 isretrieving stored data 92 from the DST execution units (i.e., the DSTNmodule). In this example, the DST execution units output encoded dataslices corresponding to data retrieval requests from the distributedtask control module 188. The de-grouping module 180 receives pillars ofslices 100 and de-groups them in accordance with control information 190from the control module 186 to produce sets of encoded data slices 218.The DS error decoding module 182 decodes, in accordance with the DSerror encoding parameters received as control information 190 from thecontrol module 186, each set of encoded data slices 218 to produce datasegments, which are aggregated into retrieved data 92. The datade-partitioning module 184 is by-passed in this operational mode via abypass signal 226 of control information 190 from the control module186.

FIG. 26 is a schematic block diagram of an embodiment of a dispersedstorage (DS) error decoding module 182 of an inbound distributed storageand task (DST) processing section. The DS error decoding module 182includes an inverse per slice security processing module 202, ade-slicing module 204, an error decoding module 206, an inverse segmentsecurity module 208, and a de-segmenting processing module 210. Thedispersed error decoding module 182 is operable to de-slice and decodeencoded slices per data segment 218 utilizing a de-slicing and decodingfunction 228 to produce a plurality of data segments that arede-segmented utilizing a de-segment function 230 to recover data 92.

In an example of operation, the inverse per slice security processingmodule 202, when enabled by the control module 186 via controlinformation 190, unsecures each encoded data slice 218 based on slicede-security information (e.g., the compliment of the slice securityinformation discussed with reference to FIG. 6) received as controlinformation 190 from the control module 186. The slice de-securityinformation includes data decompression, decryption, de-watermarking,integrity check (e.g., CRC verification, etc.), and/or any other type ofdigital security. For example, when the inverse per slice securityprocessing module 202 is enabled, it verifies integrity information(e.g., a CRC value) of each encoded data slice 218, it decrypts eachverified encoded data slice, and decompresses each decrypted encodeddata slice to produce slice encoded data. When the inverse per slicesecurity processing module 202 is not enabled, it passes the encodeddata slices 218 as the sliced encoded data or is bypassed such that theretrieved encoded data slices 218 are provided as the sliced encodeddata.

The de-slicing module 204 de-slices the sliced encoded data into encodeddata segments in accordance with a pillar width of the error correctionencoding parameters received as control information 190 from a controlmodule 186. For example, if the pillar width is five, the de-slicingmodule de-slices a set of five encoded data slices into an encoded datasegment. Alternatively, the encoded data segment may include just threeencoded data slices (e.g., when the decode threshold is 3).

The error decoding module 206 decodes the encoded data segments inaccordance with error correction decoding parameters received as controlinformation 190 from the control module 186 to produce secure datasegments. The error correction decoding parameters include identifyingan error correction encoding scheme (e.g., forward error correctionalgorithm, a Reed-Solomon based algorithm, an information dispersalalgorithm, etc.), a pillar width, a decode threshold, a read threshold,a write threshold, etc. For example, the error correction decodingparameters identify a specific error correction encoding scheme, specifya pillar width of five, and specify a decode threshold of three.

The inverse segment security processing module 208, when enabled by thecontrol module 186, unsecures the secured data segments based on segmentsecurity information received as control information 190 from thecontrol module 186. The segment security information includes datadecompression, decryption, de-watermarking, integrity check (e.g., CRC,etc.) verification, and/or any other type of digital security. Forexample, when the inverse segment security processing module is enabled,it verifies integrity information (e.g., a CRC value) of each securedata segment, it decrypts each verified secured data segment, anddecompresses each decrypted secure data segment to produce a datasegment 152. When the inverse segment security processing module 208 isnot enabled, it passes the decoded data segment 152 as the data segmentor is bypassed. The de-segmenting processing module 210 aggregates thedata segments 152 into the data 92 in accordance with controlinformation 190 from the control module 186.

FIG. 27 is a schematic block diagram of an example of a distributedstorage and task processing network (DSTN) module that includes aplurality of distributed storage and task (DST) execution units (#1through #n, where, for example, n is an integer greater than or equal tothree). Each of the DST execution units includes a DST client module 34,a controller 86, one or more DT (distributed task) execution modules 90,and memory 88.

In this example, the DSTN module stores, in the memory of the DSTexecution units, a plurality of DS (dispersed storage) encoded data(e.g., 1 through n, where n is an integer greater than or equal to two)and stores a plurality of DS encoded task codes (e.g., 1 through k,where k is an integer greater than or equal to two). The DS encoded datamay be encoded in accordance with one or more examples described withreference to FIGS. 3-19 (e.g., organized in slice groupings) or encodedin accordance with one or more examples described with reference toFIGS. 20-26 (e.g., organized in pillar groups). The data that is encodedinto the DS encoded data may be of any size and/or of any content. Forexample, the data may be one or more digital books, a copy of acompany's emails, a large-scale Internet search, a video security file,one or more entertainment video files (e.g., television programs,movies, etc.), data files, and/or any other large amount of data (e.g.,greater than a few Terabytes).

The tasks that are encoded into the DS encoded task code may be a simplefunction (e.g., a mathematical function, a logic function, an identifyfunction, a find function, a search engine function, a replace function,etc.), a complex function (e.g., compression, human and/or computerlanguage translation, text-to-voice conversion, voice-to-textconversion, etc.), multiple simple and/or complex functions, one or morealgorithms, one or more applications, etc. The tasks may be encoded intothe DS encoded task code in accordance with one or more examplesdescribed with reference to FIGS. 3-19 (e.g., organized in slicegroupings) or encoded in accordance with one or more examples describedwith reference to FIGS. 20-26 (e.g., organized in pillar groups).

In an example of operation, a DST client module of a user device or of aDST processing unit issues a DST request to the DSTN module. The DSTrequest may include a request to retrieve stored data, or a portionthereof, may include a request to store data that is included with theDST request, may include a request to perform one or more tasks onstored data, may include a request to perform one or more tasks on dataincluded with the DST request, etc. In the cases where the DST requestincludes a request to store data or to retrieve data, the client moduleand/or the DSTN module processes the request as previously discussedwith reference to one or more of FIGS. 3-19 (e.g., slice groupings)and/or 20-26 (e.g., pillar groupings). In the case where the DST requestincludes a request to perform one or more tasks on data included withthe DST request, the DST client module and/or the DSTN module processthe DST request as previously discussed with reference to one or more ofFIGS. 3-19.

In the case where the DST request includes a request to perform one ormore tasks on stored data, the DST client module and/or the DSTN moduleprocesses the DST request as will be described with reference to one ormore of FIGS. 28-39. In general, the DST client module identifies dataand one or more tasks for the DSTN module to execute upon the identifieddata. The DST request may be for a one-time execution of the task or foran on-going execution of the task. As an example of the latter, as acompany generates daily emails, the DST request may be to daily searchnew emails for inappropriate content and, if found, record the content,the email sender(s), the email recipient(s), email routing information,notify human resources of the identified email, etc.

FIG. 28 is a schematic block diagram of an example of a distributedcomputing system performing tasks on stored data. In this example, twodistributed storage and task (DST) client modules 1-2 are shown: thefirst may be associated with a user device and the second may beassociated with a DST processing unit or a high priority user device(e.g., high priority clearance user, system administrator, etc.). EachDST client module includes a list of stored data 234 and a list of taskscodes 236. The list of stored data 234 includes one or more entries ofdata identifying information, where each entry identifies data stored inthe DSTN module 22. The data identifying information (e.g., data ID)includes one or more of a data file name, a data file directory listing,DSTN addressing information of the data, a data object identifier, etc.The list of tasks 236 includes one or more entries of task codeidentifying information, when each entry identifies task codes stored inthe DSTN module 22. The task code identifying information (e.g., taskID) includes one or more of a task file name, a task file directorylisting, DSTN addressing information of the task, another type ofidentifier to identify the task, etc.

As shown, the list of data 234 and the list of tasks 236 are eachsmaller in number of entries for the first DST client module than thecorresponding lists of the second DST client module. This may occurbecause the user device associated with the first DST client module hasfewer privileges in the distributed computing system than the deviceassociated with the second DST client module. Alternatively, this mayoccur because the user device associated with the first DST clientmodule serves fewer users than the device associated with the second DSTclient module and is restricted by the distributed computing systemaccordingly. As yet another alternative, this may occur through norestraints by the distributed computing system, it just occurred becausethe operator of the user device associated with the first DST clientmodule has selected fewer data and/or fewer tasks than the operator ofthe device associated with the second DST client module.

In an example of operation, the first DST client module selects one ormore data entries 238 and one or more tasks 240 from its respectivelists (e.g., selected data ID and selected task ID). The first DSTclient module sends its selections to a task distribution module 232.The task distribution module 232 may be within a stand-alone device ofthe distributed computing system, may be within the user device thatcontains the first DST client module, or may be within the DSTN module22.

Regardless of the task distribution module's location, it generates DSTallocation information 242 from the selected task ID 240 and theselected data ID 238. The DST allocation information 242 includes datapartitioning information, task execution information, and/orintermediate result information. The task distribution module 232 sendsthe DST allocation information 242 to the DSTN module 22. Note that oneor more examples of the DST allocation information will be discussedwith reference to one or more of FIGS. 29-39.

The DSTN module 22 interprets the DST allocation information 242 toidentify the stored DS encoded data (e.g., DS error encoded data 2) andto identify the stored DS error encoded task code (e.g., DS errorencoded task code 1). In addition, the DSTN module 22 interprets the DSTallocation information 242 to determine how the data is to bepartitioned and how the task is to be partitioned. The DSTN module 22also determines whether the selected DS error encoded data 238 needs tobe converted from pillar grouping to slice grouping. If so, the DSTNmodule 22 converts the selected DS error encoded data into slicegroupings and stores the slice grouping DS error encoded data byoverwriting the pillar grouping DS error encoded data or by storing itin a different location in the memory of the DSTN module 22 (i.e., doesnot overwrite the pillar grouping DS encoded data).

The DSTN module 22 partitions the data and the task as indicated in theDST allocation information 242 and sends the portions to selected DSTexecution units of the DSTN module 22. Each of the selected DSTexecution units performs its partial task(s) on its slice groupings toproduce partial results. The DSTN module 22 collects the partial resultsfrom the selected DST execution units and provides them, as resultinformation 244, to the task distribution module. The result information244 may be the collected partial results, one or more final results asproduced by the DSTN module 22 from processing the partial results inaccordance with the DST allocation information 242, or one or moreintermediate results as produced by the DSTN module 22 from processingthe partial results in accordance with the DST allocation information242.

The task distribution module 232 receives the result information 244 andprovides one or more final results 104 therefrom to the first DST clientmodule. The final result(s) 104 may be result information 244 or aresult(s) of the task distribution module's processing of the resultinformation 244.

In concurrence with processing the selected task of the first DST clientmodule, the distributed computing system may process the selectedtask(s) of the second DST client module on the selected data(s) of thesecond DST client module. Alternatively, the distributed computingsystem may process the second DST client module's request subsequent to,or preceding, that of the first DST client module. Regardless of theordering and/or parallel processing of the DST client module requests,the second DST client module provides its selected data 238 and selectedtask 240 to a task distribution module 232. If the task distributionmodule 232 is a separate device of the distributed computing system orwithin the DSTN module, the task distribution modules 232 coupled to thefirst and second DST client modules may be the same module. The taskdistribution module 232 processes the request of the second DST clientmodule in a similar manner as it processed the request of the first DSTclient module.

FIG. 29 is a schematic block diagram of an embodiment of a taskdistribution module 232 facilitating the example of FIG. 28. The taskdistribution module 232 includes a plurality of tables it uses togenerate distributed storage and task (DST) allocation information 242for selected data and selected tasks received from a DST client module.The tables include data storage information 248, task storageinformation 250, distributed task (DT) execution module information 252,and task

sub-task mapping information 246.

The data storage information table 248 includes a data identification(ID) field 260, a data size field 262, an addressing information field264, distributed storage (DS) information 266, and may further includeother information regarding the data, how it is stored, and/or how itcan be processed. For example, DS encoded data #1 has a data ID of 1, adata size of AA (e.g., a byte size of a few Terabytes or more),addressing information of Addr_1_AA, and DS parameters of 3/5; SEG_1;and SLC_1. In this example, the addressing information may be a virtualaddress corresponding to the virtual address of the first storage word(e.g., one or more bytes) of the data and information on how tocalculate the other addresses, may be a range of virtual addresses forthe storage words of the data, physical addresses of the first storageword or the storage words of the data, may be a list of slice names ofthe encoded data slices of the data, etc. The DS parameters may includeidentity of an error encoding scheme, decode threshold/pillar width(e.g., 3/5 for the first data entry), segment security information(e.g., SEG_1), per slice security information (e.g., SLC_1), and/or anyother information regarding how the data was encoded into data slices.

The task storage information table 250 includes a task identification(ID) field 268, a task size field 270, an addressing information field272, distributed storage (DS) information 274, and may further includeother information regarding the task, how it is stored, and/or how itcan be used to process data. For example, DS encoded task #2 has a taskID of 2, a task size of XY, addressing information of Addr_2_XY, and DSparameters of 3/5; SEG_2; and SLC_2. In this example, the addressinginformation may be a virtual address corresponding to the virtualaddress of the first storage word (e.g., one or more bytes) of the taskand information on how to calculate the other addresses, may be a rangeof virtual addresses for the storage words of the task, physicaladdresses of the first storage word or the storage words of the task,may be a list of slices names of the encoded slices of the task code,etc. The DS parameters may include identity of an error encoding scheme,decode threshold/pillar width (e.g., 3/5 for the first data entry),segment security information (e.g., SEG_2), per slice securityinformation (e.g., SLC_2), and/or any other information regarding howthe task was encoded into encoded task slices. Note that the segmentand/or the per-slice security information include a type of encryption(if enabled), a type of compression (if enabled), watermarkinginformation (if enabled), and/or an integrity check scheme (if enabled).

The task

sub-task mapping information table 246 includes a task field 256 and asub-task field 258. The task field 256 identifies a task stored in thememory of a distributed storage and task network (DSTN) module and thecorresponding sub-task fields 258 indicates whether the task includessub-tasks and, if so, how many and if any of the sub-tasks are ordered.In this example, the task

sub-task mapping information table 246 includes an entry for each taskstored in memory of the DSTN module (e.g., task 1 through task k). Inparticular, this example indicates that task 1 includes 7 sub-tasks;task 2 does not include sub-tasks, and task k includes r number ofsub-tasks (where r is an integer greater than or equal to two).

The DT execution module table 252 includes a DST execution unit ID field276, a DT execution module ID field 278, and a DT execution modulecapabilities field 280. The DST execution unit ID field 276 includes theidentity of DST units in the DSTN module. The DT execution module IDfield 278 includes the identity of each DT execution unit in each DSTunit. For example, DST unit 1 includes three DT executions modules(e.g., 1_1, 1_2, and 1_3). The DT execution capabilities field 280includes identity of the capabilities of the corresponding DT executionunit. For example, DT execution module 1_1 includes capabilities X,where X includes one or more of MIPS capabilities, processing resources(e.g., quantity and capability of microprocessors, CPUs, digital signalprocessors, co-processor, microcontrollers, arithmetic logic circuitry,and/or any other analog and/or digital processing circuitry),availability of the processing resources, memory information (e.g.,type, size, availability, etc.), and/or any information germane toexecuting one or more tasks.

From these tables, the task distribution module 232 generates the DSTallocation information 242 to indicate where the data is stored, how topartition the data, where the task is stored, how to partition the task,which DT execution units should perform which partial task on which datapartitions, where and how intermediate results are to be stored, etc. Ifmultiple tasks are being performed on the same data or different data,the task distribution module factors such information into itsgeneration of the DST allocation information.

FIG. 30 is a diagram of a specific example of a distributed computingsystem performing tasks on stored data as a task flow 318. In thisexample, selected data 92 is data 2 and selected tasks are tasks 1, 2,and 3. Task 1 corresponds to analyzing translation of data from onelanguage to another (e.g., human language or computer language); task 2corresponds to finding specific words and/or phrases in the data; andtask 3 corresponds to finding specific translated words and/or phrasesin translated data.

In this example, task 1 includes 7 sub-tasks: task 1_1—identifynon-words (non-ordered); task 1_2—identify unique words (non-ordered);task 1_3—translate (non-ordered); task 1_4—translate back (ordered aftertask 1_3); task 1_5—compare to ID errors (ordered after task 1-4); task1_6—determine non-word translation errors (ordered after task 1_5 and1_1); and task 1_7—determine correct translations (ordered after 1_5 and1_2). The sub-task further indicates whether they are an ordered task(i.e., are dependent on the outcome of another task) or non-order (i.e.,are independent of the outcome of another task). Task 2 does not includesub-tasks and task 3 includes two sub-tasks: task 3_1 translate; andtask 3_2 find specific word or phrase in translated data.

In general, the three tasks collectively are selected to analyze datafor translation accuracies, translation errors, translation anomalies,occurrence of specific words or phrases in the data, and occurrence ofspecific words or phrases on the translated data. Graphically, the data92 is translated 306 into translated data 282; is analyzed for specificwords and/or phrases 300 to produce a list of specific words and/orphrases 286; is analyzed for non-words 302 (e.g., not in a referencedictionary) to produce a list of non-words 290; and is analyzed forunique words 316 included in the data 92 (i.e., how many different wordsare included in the data) to produce a list of unique words 298. Each ofthese tasks is independent of each other and can therefore be processedin parallel if desired.

The translated data 282 is analyzed (e.g., sub-task 3_2) for specifictranslated words and/or phrases 304 to produce a list of specifictranslated words and/or phrases 288. The translated data 282 istranslated back 308 (e.g., sub-task 1_4) into the language of theoriginal data to produce re-translated data 284. These two tasks aredependent on the translate task (e.g., task 1_3) and thus must beordered after the translation task, which may be in a pipelined orderingor a serial ordering. The re-translated data 284 is then compared 310with the original data 92 to find words and/or phrases that did nottranslate (one way and/or the other) properly to produce a list ofincorrectly translated words 294. As such, the comparing task (e.g.,sub-task 1_5) 310 is ordered after the translation 306 andre-translation tasks 308 (e.g., sub-tasks 1_3 and 1_4).

The list of words incorrectly translated 294 is compared 312 to the listof non-words 290 to identify words that were not properly translatedbecause the words are non-words to produce a list of errors due tonon-words 292. In addition, the list of words incorrectly translated 294is compared 314 to the list of unique words 298 to identify unique wordsthat were properly translated to produce a list of correctly translatedwords 296. The comparison may also identify unique words that were notproperly translated to produce a list of unique words that were notproperly translated. Note that each list of words (e.g., specific wordsand/or phrases, non-words, unique words, translated words and/orphrases, etc.,) may include the word and/or phrase, how many times it isused, where in the data it is used, and/or any other informationrequested regarding a word and/or phrase.

FIG. 31 is a schematic block diagram of an example of a distributedstorage and task processing network (DSTN) module storing data and taskcodes for the example of FIG. 30. As shown, DS encoded data 2 is storedas encoded data slices across the memory (e.g., stored in memories 88)of DST execution units 1-5; the DS encoded task code 1 (of task 1) andDS encoded task 3 are stored as encoded task slices across the memory ofDST execution units 1-5; and DS encoded task code 2 (of task 2) isstored as encoded task slices across the memory of DST execution units3-7. As indicated in the data storage information table and the taskstorage information table of FIG. 29, the respective data/task has DSparameters of 3/5 for their decode threshold/pillar width; hencespanning the memory of five DST execution units.

FIG. 32 is a diagram of an example of distributed storage and task (DST)allocation information 242 for the example of FIG. 30. The DSTallocation information 242 includes data partitioning information 320,task execution information 322, and intermediate result information 324.The data partitioning information 320 includes the data identifier (ID),the number of partitions to split the data into, address information foreach data partition, and whether the DS encoded data has to betransformed from pillar grouping to slice grouping. The task executioninformation 322 includes tabular information having a taskidentification field 326, a task ordering field 328, a data partitionfield ID 330, and a set of DT execution modules 332 to use for thedistributed task processing per data partition. The intermediate resultinformation 324 includes tabular information having a name ID field 334,an ID of the DST execution unit assigned to process the correspondingintermediate result 336, a scratch pad storage field 338, and anintermediate result storage field 340.

Continuing with the example of FIG. 30, where tasks 1-3 are to bedistributedly performed on data 2, the data partitioning informationincludes the ID of data 2. In addition, the task distribution moduledetermines whether the DS encoded data 2 is in the proper format fordistributed computing (e.g., was stored as slice groupings). If not, thetask distribution module indicates that the DS encoded data 2 formatneeds to be changed from the pillar grouping format to the slicegrouping format, which will be done by the DSTN module. In addition, thetask distribution module determines the number of partitions to dividethe data into (e.g., 2_1 through 2_z) and addressing information foreach partition.

The task distribution module generates an entry in the task executioninformation section for each sub-task to be performed. For example, task1_1 (e.g., identify non-words on the data) has no task ordering (i.e.,is independent of the results of other sub-tasks), is to be performed ondata partitions 2_1 through 2_z by DT execution modules 1_1, 2_1, 3_1,4_1, and 5_1. For instance, DT execution modules 1_1, 2_1, 3_1, 4_1, and5_1 search for non-words in data partitions 2_1 through 2_z to producetask 1_1 intermediate results (R1-1, which is a list of non-words). Task1_2 (e.g., identify unique words) has similar task execution informationas task 1_1 to produce task 1_2 intermediate results (R1-2, which is thelist of unique words).

Task 1_3 (e.g., translate) includes task execution information as beingnon-ordered (i.e., is independent), having DT execution modules 1_1,2_1, 3_1, 4_1, and 5_1 translate data partitions 2_1 through 2_4 andhaving DT execution modules 1_2, 2_2, 3_2, 4_2, and 5_2 translate datapartitions 2_5 through 2_z to produce task 1_3 intermediate results(R1-3, which is the translated data). In this example, the datapartitions are grouped, where different sets of DT execution modulesperform a distributed sub-task (or task) on each data partition group,which allows for further parallel processing.

Task 1_4 (e.g., translate back) is ordered after task 1_3 and is to beexecuted on task 1_3's intermediate result (e.g., R1-3_1) (e.g., thetranslated data). DT execution modules 1_1, 2_1, 3_1, 4_1, and 5_1 areallocated to translate back task 1_3 intermediate result partitionsR1-3_1 through R1-3_4 and DT execution modules 1_2, 2_2, 6_1, 7_1, and7_2 are allocated to translate back task 1_3 intermediate resultpartitions R1-3_5 through R1-3_z to produce task 1-4 intermediateresults (R1-4, which is the translated back data).

Task 1_5 (e.g., compare data and translated data to identify translationerrors) is ordered after task 1_4 and is to be executed on task 1_4'sintermediate results (R4-1) and on the data. DT execution modules 1_1,2_1, 3_1, 4_1, and 5_1 are allocated to compare the data partitions (2_1through 2_z) with partitions of task 1-4 intermediate results partitionsR1-4_1 through R1-4_z to produce task 1_5 intermediate results (R1-5,which is the list words translated incorrectly).

Task 1_6 (e.g., determine non-word translation errors) is ordered aftertasks 1_1 and 1_5 and is to be executed on tasks 1_1's and 1_5'sintermediate results (R1-1 and R1-5). DT execution modules 1_1, 2_1,3_1, 4_1, and 5_1 are allocated to compare the partitions of task 1_1intermediate results (R1-1_1 through R1-1_z) with partitions of task 1-5intermediate results partitions (R1-5_1 through R1-5_z) to produce task1_6 intermediate results (R1-6, which is the list translation errors dueto non-words).

Task 1_7 (e.g., determine words correctly translated) is ordered aftertasks 1_2 and 1_5 and is to be executed on tasks 1_2's and 1_5'sintermediate results (R1-1 and R1-5). DT execution modules 1_2, 2_2,3_2, 4_2, and 5_2 are allocated to compare the partitions of task 1_2intermediate results (R1-2_1 through R1-2_z) with partitions of task 1-5intermediate results partitions (R1-5_1 through R1-5_z) to produce task1_7 intermediate results (R1-7, which is the list of correctlytranslated words).

Task 2 (e.g., find specific words and/or phrases) has no task ordering(i.e., is independent of the results of other sub-tasks), is to beperformed on data partitions 2_1 through 2_z by DT execution modules3_1, 4_1, 5_1, 6_1, and 7_1. For instance, DT execution modules 3_1,4_1, 5_1, 6_1, and 7_1 search for specific words and/or phrases in datapartitions 2_1 through 2_z to produce task 2 intermediate results (R2,which is a list of specific words and/or phrases).

Task 3_2 (e.g., find specific translated words and/or phrases) isordered after task 1_3 (e.g., translate) is to be performed onpartitions R1-3_1 through R1-3_z by DT execution modules 1_2, 2_2, 3_2,4_2, and 5_2. For instance, DT execution modules 1_2, 2_2, 3_2, 4_2, and5_2 search for specific translated words and/or phrases in thepartitions of the translated data (R1-3_1 through R1-3_z) to producetask 3_2 intermediate results (R3-2, which is a list of specifictranslated words and/or phrases).

For each task, the intermediate result information indicates which DSTunit is responsible for overseeing execution of the task and, if needed,processing the partial results generated by the set of allocated DTexecution units. In addition, the intermediate result informationindicates a scratch pad memory for the task and where the correspondingintermediate results are to be stored. For example, for intermediateresult R1-1 (the intermediate result of task 1_1), DST unit 1 isresponsible for overseeing execution of the task 1_1 and coordinatesstorage of the intermediate result as encoded intermediate result slicesstored in memory of DST execution units 1-5. In general, the scratch padis for storing non-DS encoded intermediate results and the intermediateresult storage is for storing DS encoded intermediate results.

FIGS. 33-38 are schematic block diagrams of the distributed storage andtask network (DSTN) module performing the example of FIG. 30. In FIG.33, the DSTN module accesses the data 92 and partitions it into aplurality of partitions 1-z in accordance with distributed storage andtask network (DST) allocation information. For each data partition, theDSTN identifies a set of its DT (distributed task) execution modules 90to perform the task (e.g., identify non-words (i.e., not in a referencedictionary) within the data partition) in accordance with the DSTallocation information. From data partition to data partition, the setof DT execution modules 90 may be the same, different, or a combinationthereof (e.g., some data partitions use the same set while other datapartitions use different sets).

For the first data partition, the first set of DT execution modules(e.g., 1_1, 2_1, 3_1, 4_1, and 5_1 per the DST allocation information ofFIG. 32) executes task 1_1 to produce a first partial result 102 ofnon-words found in the first data partition. The second set of DTexecution modules (e.g., 1_1, 2_1, 3_1, 4_1, and 5_1 per the DSTallocation information of FIG. 32) executes task 1_1 to produce a secondpartial result 102 of non-words found in the second data partition. Thesets of DT execution modules (as per the DST allocation information)perform task 1_1 on the data partitions until the “z” set of DTexecution modules performs task 1_1 on the “zth” data partition toproduce a “zth” partial result 102 of non-words found in the “zth” datapartition.

As indicated in the DST allocation information of FIG. 32, DST executionunit 1 is assigned to process the first through “zth” partial results toproduce the first intermediate result (R1-1), which is a list ofnon-words found in the data. For instance, each set of DT executionmodules 90 stores its respective partial result in the scratchpad memoryof DST execution unit 1 (which is identified in the DST allocation ormay be determined by DST execution unit 1). A processing module of DSTexecution 1 is engaged to aggregate the first through “zth” partialresults to produce the first intermediate result (e.g., R1_1). Theprocessing module stores the first intermediate result as non-DS errorencoded data in the scratchpad memory or in another section of memory ofDST execution unit 1.

DST execution unit 1 engages its DST client module to slice groupingbased DS error encode the first intermediate result (e.g., the list ofnon-words). To begin the encoding, the DST client module determineswhether the list of non-words is of a sufficient size to partition(e.g., greater than a Terabyte). If yes, it partitions the firstintermediate result (R1-1) into a plurality of partitions (e.g., R1-1_1through R1-1_m). If the first intermediate result is not of sufficientsize to partition, it is not partitioned.

For each partition of the first intermediate result, or for the firstintermediate result, the DST client module uses the DS error encodingparameters of the data (e.g., DS parameters of data 2, which includes3/5 decode threshold/pillar width ratio) to produce slice groupings. Theslice groupings are stored in the intermediate result memory (e.g.,allocated memory in the memories of DST execution units 1-5).

In FIG. 34, the DSTN module is performing task 1_2 (e.g., find uniquewords) on the data 92. To begin, the DSTN module accesses the data 92and partitions it into a plurality of partitions 1-z in accordance withthe DST allocation information or it may use the data partitions of task1_1 if the partitioning is the same. For each data partition, the DSTNidentifies a set of its DT execution modules to perform task 1_2 inaccordance with the DST allocation information. From data partition todata partition, the set of DT execution modules may be the same,different, or a combination thereof. For the data partitions, theallocated set of DT execution modules executes task 1_2 to produce apartial results (e.g., 1^(st) through “zth”) of unique words found inthe data partitions.

As indicated in the DST allocation information of FIG. 32, DST executionunit 1 is assigned to process the first through “zth” partial results102 of task 1_2 to produce the second intermediate result (R1-2), whichis a list of unique words found in the data 92. The processing module ofDST execution 1 is engaged to aggregate the first through “zth” partialresults of unique words to produce the second intermediate result. Theprocessing module stores the second intermediate result as non-DS errorencoded data in the scratchpad memory or in another section of memory ofDST execution unit 1.

DST execution unit 1 engages its DST client module to slice groupingbased DS error encode the second intermediate result (e.g., the list ofnon-words). To begin the encoding, the DST client module determineswhether the list of unique words is of a sufficient size to partition(e.g., greater than a Terabyte). If yes, it partitions the secondintermediate result (R1-2) into a plurality of partitions (e.g., R1-2_1through R1-2_m). If the second intermediate result is not of sufficientsize to partition, it is not partitioned.

For each partition of the second intermediate result, or for the secondintermediate results, the DST client module uses the DS error encodingparameters of the data (e.g., DS parameters of data 2, which includes3/5 decode threshold/pillar width ratio) to produce slice groupings. Theslice groupings are stored in the intermediate result memory (e.g.,allocated memory in the memories of DST execution units 1-5).

In FIG. 35, the DSTN module is performing task 1_3 (e.g., translate) onthe data 92. To begin, the DSTN module accesses the data 92 andpartitions it into a plurality of partitions 1-z in accordance with theDST allocation information or it may use the data partitions of task 1_1if the partitioning is the same. For each data partition, the DSTNidentifies a set of its DT execution modules to perform task 1_3 inaccordance with the DST allocation information (e.g., DT executionmodules 1_1, 2_1, 3_1, 4_1, and 5_1 translate data partitions 2_1through 2_4 and DT execution modules 1_2, 2_2, 3_2, 4_2, and 5_2translate data partitions 2_5 through 2_z). For the data partitions, theallocated set of DT execution modules 90 executes task 1_3 to producepartial results 102 (e.g., 1^(st) through “zth”) of translated data.

As indicated in the DST allocation information of FIG. 32, DST executionunit 2 is assigned to process the first through “zth” partial results oftask 1_3 to produce the third intermediate result (R1-3), which istranslated data. The processing module of DST execution 2 is engaged toaggregate the first through “zth” partial results of translated data toproduce the third intermediate result. The processing module stores thethird intermediate result as non-DS error encoded data in the scratchpadmemory or in another section of memory of DST execution unit 2.

DST execution unit 2 engages its DST client module to slice groupingbased DS error encode the third intermediate result (e.g., translateddata). To begin the encoding, the DST client module partitions the thirdintermediate result (R1-3) into a plurality of partitions (e.g., R1-3_1through R1-3_y). For each partition of the third intermediate result,the DST client module uses the DS error encoding parameters of the data(e.g., DS parameters of data 2, which includes 3/5 decodethreshold/pillar width ratio) to produce slice groupings. The slicegroupings are stored in the intermediate result memory (e.g., allocatedmemory in the memories of DST execution units 2-6 per the DST allocationinformation).

As is further shown in FIG. 35, the DSTN module is performing task 1_4(e.g., retranslate) on the translated data of the third intermediateresult. To begin, the DSTN module accesses the translated data (from thescratchpad memory or from the intermediate result memory and decodes it)and partitions it into a plurality of partitions in accordance with theDST allocation information. For each partition of the third intermediateresult, the DSTN identifies a set of its DT execution modules 90 toperform task 1_4 in accordance with the DST allocation information(e.g., DT execution modules 1_1, 2_1, 3_1, 4_1, and 5_1 are allocated totranslate back partitions R1-3_1 through R1-3_4 and DT execution modules1_2, 2_2, 6_1, 7_1, and 7_2 are allocated to translate back partitionsR1-3_5 through R1-3_z). For the partitions, the allocated set of DTexecution modules executes task 1_4 to produce partial results 102(e.g., 1^(st) through “zth”) of re-translated data.

As indicated in the DST allocation information of FIG. 32, DST executionunit 3 is assigned to process the first through “zth” partial results oftask 1_4 to produce the fourth intermediate result (R1-4), which isretranslated data. The processing module of DST execution 3 is engagedto aggregate the first through “zth” partial results of retranslateddata to produce the fourth intermediate result. The processing modulestores the fourth intermediate result as non-DS error encoded data inthe scratchpad memory or in another section of memory of DST executionunit 3.

DST execution unit 3 engages its DST client module to slice groupingbased DS error encode the fourth intermediate result (e.g., retranslateddata). To begin the encoding, the DST client module partitions thefourth intermediate result (R1-4) into a plurality of partitions (e.g.,R1-4_1 through R1-4_z). For each partition of the fourth intermediateresult, the DST client module uses the DS error encoding parameters ofthe data (e.g., DS parameters of data 2, which includes 3/5 decodethreshold/pillar width ratio) to produce slice groupings. The slicegroupings are stored in the intermediate result memory (e.g., allocatedmemory in the memories of DST execution units 3-7 per the DST allocationinformation).

In FIG. 36, a distributed storage and task network (DSTN) module isperforming task 1_5 (e.g., compare) on data 92 and retranslated data ofFIG. 35. To begin, the DSTN module accesses the data 92 and partitionsit into a plurality of partitions in accordance with the DST allocationinformation or it may use the data partitions of task 1_1 if thepartitioning is the same. The DSTN module also accesses the retranslateddata from the scratchpad memory, or from the intermediate result memoryand decodes it, and partitions it into a plurality of partitions inaccordance with the DST allocation information. The number of partitionsof the retranslated data corresponds to the number of partitions of thedata.

For each pair of partitions (e.g., data partition 1 and retranslateddata partition 1), the DSTN identifies a set of its DT execution modules90 to perform task 1_5 in accordance with the DST allocation information(e.g., DT execution modules 1_1, 2_1, 3_1, 4_1, and 5_1). For each pairof partitions, the allocated set of DT execution modules executes task1_5 to produce partial results 102 (e.g., 1^(st) through “zth”) of alist of incorrectly translated words and/or phrases.

As indicated in the DST allocation information of FIG. 32, DST executionunit 1 is assigned to process the first through “zth” partial results oftask 1_5 to produce the fifth intermediate result (R1-5), which is thelist of incorrectly translated words and/or phrases. In particular, theprocessing module of DST execution 1 is engaged to aggregate the firstthrough “zth” partial results of the list of incorrectly translatedwords and/or phrases to produce the fifth intermediate result. Theprocessing module stores the fifth intermediate result as non-DS errorencoded data in the scratchpad memory or in another section of memory ofDST execution unit 1.

DST execution unit 1 engages its DST client module to slice groupingbased DS error encode the fifth intermediate result. To begin theencoding, the DST client module partitions the fifth intermediate result(R1-5) into a plurality of partitions (e.g., R1-5_1 through R1-5_z). Foreach partition of the fifth intermediate result, the DST client moduleuses the DS error encoding parameters of the data (e.g., DS parametersof data 2, which includes 3/5 decode threshold/pillar width ratio) toproduce slice groupings. The slice groupings are stored in theintermediate result memory (e.g., allocated memory in the memories ofDST execution units 1-5 per the DST allocation information).

As is further shown in FIG. 36, the DSTN module is performing task 1_6(e.g., translation errors due to non-words) on the list of incorrectlytranslated words and/or phrases (e.g., the fifth intermediate resultR1-5) and the list of non-words (e.g., the first intermediate resultR1-1). To begin, the DSTN module accesses the lists and partitions theminto a corresponding number of partitions.

For each pair of partitions (e.g., partition R1-1_1 and partitionR1-5_1), the DSTN identifies a set of its DT execution modules 90 toperform task 1_6 in accordance with the DST allocation information(e.g., DT execution modules 1_1, 2_1, 3_1, 4_1, and 5_1). For each pairof partitions, the allocated set of DT execution modules executes task1_6 to produce partial results 102 (e.g., 1^(st) through “zth”) of alist of incorrectly translated words and/or phrases due to non-words.

As indicated in the DST allocation information of FIG. 32, DST executionunit 2 is assigned to process the first through “zth” partial results oftask 1_6 to produce the sixth intermediate result (R1-6), which is thelist of incorrectly translated words and/or phrases due to non-words. Inparticular, the processing module of DST execution 2 is engaged toaggregate the first through “zth” partial results of the list ofincorrectly translated words and/or phrases due to non-words to producethe sixth intermediate result. The processing module stores the sixthintermediate result as non-DS error encoded data in the scratchpadmemory or in another section of memory of DST execution unit 2.

DST execution unit 2 engages its DST client module to slice groupingbased DS error encode the sixth intermediate result. To begin theencoding, the DST client module partitions the sixth intermediate result(R1-6) into a plurality of partitions (e.g., R1-6_1 through R1-6_z). Foreach partition of the sixth intermediate result, the DST client moduleuses the DS error encoding parameters of the data (e.g., DS parametersof data 2, which includes 3/5 decode threshold/pillar width ratio) toproduce slice groupings. The slice groupings are stored in theintermediate result memory (e.g., allocated memory in the memories ofDST execution units 2-6 per the DST allocation information).

As is still further shown in FIG. 36, the DSTN module is performing task1_7 (e.g., correctly translated words and/or phrases) on the list ofincorrectly translated words and/or phrases (e.g., the fifthintermediate result R1-5) and the list of unique words (e.g., the secondintermediate result R1-2). To begin, the DSTN module accesses the listsand partitions them into a corresponding number of partitions.

For each pair of partitions (e.g., partition R1-2_1 and partitionR1-5_1), the DSTN identifies a set of its DT execution modules 90 toperform task 1_7 in accordance with the DST allocation information(e.g., DT execution modules 1_2, 2_2, 3_2, 4_2, and 5_2). For each pairof partitions, the allocated set of DT execution modules executes task1_7 to produce partial results 102 (e.g., 1^(st) through “zth”) of alist of correctly translated words and/or phrases.

As indicated in the DST allocation information of FIG. 32, DST executionunit 3 is assigned to process the first through “zth” partial results oftask 1_7 to produce the seventh intermediate result (R1-7), which is thelist of correctly translated words and/or phrases. In particular, theprocessing module of DST execution 3 is engaged to aggregate the firstthrough “zth” partial results of the list of correctly translated wordsand/or phrases to produce the seventh intermediate result. Theprocessing module stores the seventh intermediate result as non-DS errorencoded data in the scratchpad memory or in another section of memory ofDST execution unit 3.

DST execution unit 3 engages its DST client module to slice groupingbased DS error encode the seventh intermediate result. To begin theencoding, the DST client module partitions the seventh intermediateresult (R1-7) into a plurality of partitions (e.g., R1-7_1 throughR1-7_z). For each partition of the seventh intermediate result, the DSTclient module uses the DS error encoding parameters of the data (e.g.,DS parameters of data 2, which includes 3/5 decode threshold/pillarwidth ratio) to produce slice groupings. The slice groupings are storedin the intermediate result memory (e.g., allocated memory in thememories of DST execution units 3-7 per the DST allocation information).

In FIG. 37, the distributed storage and task network (DSTN) module isperforming task 2 (e.g., find specific words and/or phrases) on the data92. To begin, the DSTN module accesses the data and partitions it into aplurality of partitions 1-z in accordance with the DST allocationinformation or it may use the data partitions of task 1_1 if thepartitioning is the same. For each data partition, the DSTN identifies aset of its DT execution modules 90 to perform task 2 in accordance withthe DST allocation information. From data partition to data partition,the set of DT execution modules may be the same, different, or acombination thereof. For the data partitions, the allocated set of DTexecution modules executes task 2 to produce partial results 102 (e.g.,1^(st) through “zth”) of specific words and/or phrases found in the datapartitions.

As indicated in the DST allocation information of FIG. 32, DST executionunit 7 is assigned to process the first through “zth” partial results oftask 2 to produce task 2 intermediate result (R2), which is a list ofspecific words and/or phrases found in the data. The processing moduleof DST execution 7 is engaged to aggregate the first through “zth”partial results of specific words and/or phrases to produce the task 2intermediate result. The processing module stores the task 2intermediate result as non-DS error encoded data in the scratchpadmemory or in another section of memory of DST execution unit 7.

DST execution unit 7 engages its DST client module to slice groupingbased DS error encode the task 2 intermediate result. To begin theencoding, the DST client module determines whether the list of specificwords and/or phrases is of a sufficient size to partition (e.g., greaterthan a Terabyte). If yes, it partitions the task 2 intermediate result(R2) into a plurality of partitions (e.g., R2_1 through R2_m). If thetask 2 intermediate result is not of sufficient size to partition, it isnot partitioned.

For each partition of the task 2 intermediate result, or for the task 2intermediate results, the DST client module uses the DS error encodingparameters of the data (e.g., DS parameters of data 2, which includes3/5 decode threshold/pillar width ratio) to produce slice groupings. Theslice groupings are stored in the intermediate result memory (e.g.,allocated memory in the memories of DST execution units 1-4, and 7).

In FIG. 38, the distributed storage and task network (DSTN) module isperforming task 3 (e.g., find specific translated words and/or phrases)on the translated data (R1-3). To begin, the DSTN module accesses thetranslated data (from the scratchpad memory or from the intermediateresult memory and decodes it) and partitions it into a plurality ofpartitions in accordance with the DST allocation information. For eachpartition, the DSTN identifies a set of its DT execution modules toperform task 3 in accordance with the DST allocation information. Frompartition to partition, the set of DT execution modules may be the same,different, or a combination thereof. For the partitions, the allocatedset of DT execution modules 90 executes task 3 to produce partialresults 102 (e.g., 1^(st) through “zth”) of specific translated wordsand/or phrases found in the data partitions.

As indicated in the DST allocation information of FIG. 32, DST executionunit 5 is assigned to process the first through “zth” partial results oftask 3 to produce task 3 intermediate result (R3), which is a list ofspecific translated words and/or phrases found in the translated data.In particular, the processing module of DST execution 5 is engaged toaggregate the first through “zth” partial results of specific translatedwords and/or phrases to produce the task 3 intermediate result. Theprocessing module stores the task 3 intermediate result as non-DS errorencoded data in the scratchpad memory or in another section of memory ofDST execution unit 7.

DST execution unit 5 engages its DST client module to slice groupingbased DS error encode the task 3 intermediate result. To begin theencoding, the DST client module determines whether the list of specifictranslated words and/or phrases is of a sufficient size to partition(e.g., greater than a Terabyte). If yes, it partitions the task 3intermediate result (R3) into a plurality of partitions (e.g., R3_1through R3_m). If the task 3 intermediate result is not of sufficientsize to partition, it is not partitioned.

For each partition of the task 3 intermediate result, or for the task 3intermediate results, the DST client module uses the DS error encodingparameters of the data (e.g., DS parameters of data 2, which includes3/5 decode threshold/pillar width ratio) to produce slice groupings. Theslice groupings are stored in the intermediate result memory (e.g.,allocated memory in the memories of DST execution units 1-4, 5, and 7).

FIG. 39 is a diagram of an example of combining result information intofinal results 104 for the example of FIG. 30. In this example, theresult information includes the list of specific words and/or phrasesfound in the data (task 2 intermediate result), the list of specifictranslated words and/or phrases found in the data (task 3 intermediateresult), the list of non-words found in the data (task 1 firstintermediate result R1-1), the list of unique words found in the data(task 1 second intermediate result R1-2), the list of translation errorsdue to non-words (task 1 sixth intermediate result R1-6), and the listof correctly translated words and/or phrases (task 1 seventhintermediate result R1-7). The task distribution module provides theresult information to the requesting DST client module as the results104.

FIGS. 40A and 40B are a schematic block diagram of an embodiment of adispersed storage network (DSN) that includes the outbound dispersedstorage and task (DST) processing 80 of FIG. 3, the inbound DSTprocessing 82 of FIG. 3, the network 24 of FIG. 1, and a DST execution(EX) unit 350. The DST execution unit set 350 includes a set of DSTexecution units 1-n. Each DST execution unit may be implementedutilizing the DST execution unit 36 of FIG. 1. Hereafter, a DSTexecution unit may be referred to interchangeably as a storage unit andthe set of DST execution units may be interchangeably referred to as aset of storage units.

The outbound DST processing 80 includes an error encoding 1, an errorencoding 2, the per slice security processing 150 of FIG. 6, and thesegment security processing 144 of FIG. 6. The error encoding 1 anderror encoding 2 may each be implemented utilizing the error encoding146 of FIG. 6. The per slice security processing 150 includes a keygenerator (KEYGEN) and a set of crypto modules (CRYPTO) 1-n. The segmentsecurity processing 144 includes an all or nothing transform (AONT)module 352. The inbound DST processing 82 includes an error decoding 1,an error decoding 2, the inverse per slice security processing 202 ofFIG. 16, and the inverse segment security processing 208 of FIG. 16. Theerror decoding 1 and error decoding 2 may be implemented utilizing theerror decoding 206 of FIG. 16. The inverse per slice security processing202 includes the key generator and the set of crypto modules 1-n. Theinverse segment security processing 208 includes the AONT module 352.

The DSN functions to access data 354 stored in the DST execution unitset 350. The accessing includes storing the data 354 and retrievingstored data to produce recovered data. FIG. 40A illustrates an exampleof operation of the storing of the data 354 where the outbound DSTprocessing 80 receives the data 354 for storage. Having received thedata 354 for storage, the outbound DST processing 80 divides the data354 into a plurality of data units. As a specific example, the errorencoding 2 dispersed storage error encodes the data 354 to produce aplurality of encoded data slices as the plurality of data units. Forinstance, the error encoding 2 dispersed storage error encodes the data354 to produce a set of encoded data slices 1-n, where the encodingincludes matrix multiplying the data 354 by an encoding matrix where afirst decode threshold number of rows includes a unity matrix to producethe set of encoded data slices where a first decode threshold number ofencoded data slices includes substantially equal divisions of the data354.

With the data 354 divided into the plurality of data units, the keygenerator generates a plurality of encryption keys from a master key 356associated with the data 354 and a data identifier (ID) 358 associatedwith the data 354. The data identifier 358 includes one or more of adata name (e.g., a name associated with the data 354), a user password,a personal identification number, a plurality of data unit names (e.g.,a set of slice names 1-n associated with the set of encoded data slices1-n), and a random value. The outbound DST processing 80 may obtain themaster key 356 by at least one of generating the master key 356 based ona random number, retrieving the master key 356, and receiving the masterkey 356. As a specific example of the generating the plurality ofencryption keys, the key generator performs a one-way deterministicfunction on the master key 356 and the plurality of data unit names(e.g., slice names 1-n) to produce the plurality of encryption keys(e.g., keys 1-n), where the data identifier 358 includes the pluralityof data unit names. As another specific example of the generating theplurality of encryption keys 1-n, the key generator performs a series ofone-way deterministic functions (e.g., functions 1-n (on the master key356 and the data identifier 358 to produce the plurality of encryptionkeys (e.g., the keys 1-n). The deterministic function may include one ormore of a hash based message authentication code function, a hashingfunction, a sponge function, a mask generating function, and a logicalfunction.

With the plurality of encryption keys generated, the set of cryptomodules 1-n encrypts the plurality of data units using the plurality ofencryption keys to produce a plurality of encrypted data units. Forexample, crypto 1 encrypts slice (SLC) 1 using a key 1 of the keys 1-nto produce an encrypted slice (ESLC) 1, etc. Having produced theplurality of encrypted data units, the outbound DST processing 80 sendsthe plurality of encrypted data units to a first set of storage units ofthe DSN for storage. For example, the outbound DST processing 80 sends,via the network 24, the encrypted data slices 1-n to the set of DSTexecution units 1-n for storage.

Having stored the plurality of encrypted data units, the outbound DSTprocessing 80 encodes the master key 356 to produce a plurality ofencoded master key units (e.g., a set of key slices 1-n). As a specificexample, the AONT module 352 of the segment security processing 144performs an all-or-nothing transformation on the master key 356 toproduce a secure master key (secured MKEY) 360. For instance, the AONTmodule 352 encrypts the master key 356 utilizing another random key toproduce a temporary encrypted key, performs a deterministic function onthe temporary encrypted key to produce a digest, masks the other randomkey using the digest to produce a masked key (e.g., applies an exclusiveOR function), and combines (e.g., appends, interleaves) the masked keywith the temporary encrypted key to produce the secure master key 360.Having produced the secure master key, the error encoding 1 dispersedstorage error encodes the secure master key 360 to produce a pluralityof encoded master key slices as the plurality of encoded master keyunits (e.g., key slices 1-n).

As another specific example of producing the plurality of encoded masterkey units, the outbound DST processing 80 performs a Shamir secretsharing encoding function on the master key 356 to produce a pluralityof secret master key shares as the plurality of encoded master key units(e.g., key slices 1-n). Having produced the plurality of encoded masterkey units, the outbound DST processing 80 sends, via the network 24, theplurality of encoded master key units to a second set of storage unitsof the DSN for storage, where the first and second sets of storage unitsmay include at least one storage unit in common. For instance, the firstand second sets of storage units includes a set of storage units incommon when the outbound DST processing 80 sends the plurality ofencrypted data units and the plurality of encoded master key units tothe set of DST execution units 1-n.

FIG. 40B illustrates an example of operation of the retrieving of thedata where the inbound DST processing 82 receives a request to retrievea data unit of the plurality of data units. For instance, the inboundDST processing 82 receives a request from a requesting entity toretrieve data slice 2 only. In another instance, the inbound DSTprocessing 82 receives a request from the requesting entity to retrievethe data 354. Having received the request to retrieve the dating unit,the inbound DST processing 82 retrieves an encrypted data unit of theplurality of encrypted data units from a storage unit of the first setof storage units, where the encrypted data unit corresponds to the dataunit. For example, the inbound DST processing 82 issues, via the network24, a read slice request to the DST execution unit 2, where the readslice request includes a slice name corresponding to the encrypted dataslice 2, and receives the encrypted data slice 2 as an encrypted dataslice 360. When recovering the data 354, the inbound DST processing 82retrieves at least a decode threshold number of encrypted data slices360.

Having retrieved the encrypted data unit (e.g., encrypted data slice 2),the inbound DST processing 82 retrieves at least some of the pluralityof encoded master key units from the second set of storage units. Forexample, the inbound DST processing 82 issues, via the network 24, atleast a decode threshold number of read slice requests to the DSTexecution units 1-n, where the at least a decode threshold number ofread slice requests includes slice names corresponding to a decodethreshold number of key slices 362, and receives at least a decodethreshold number of key slices 362.

Having received the at least some of the plurality of encoded master keyunits, inbound DST processing 82 decodes the at least some of theplurality of encoded master key units to produce a recovered master key366. For example, the error decoding 1 decodes the received at least adecode threshold number of key slices 364 to produce a recovered securedmaster key 364, the AONT module 352 of the inverse segment securityprocessing 208 performs a reverse all or nothing transform function onthe recovered secured master key 364 to produce the recovered master key366. For instance, the AONT module 352 de-combines the masked key andthe encrypted key from the recovered secured master key 364, performs adeterministic function on the encrypted key to reproduce the digest,de-masks masked key using the digest (e.g., applies the exclusive ORfunction) to reproduce the other random key, and decrypts the encryptedkey using the reproduced other random key to produce the recoveredmaster key 366.

With the recovered master key 366 produced, the key generator of theinverse per slice security processing 202 generates an encryption key ofthe plurality of encryption keys from the recovered master key 366 andthe data identifier 358 (e.g., obtained with the request to retrieve).For example, the key generator performs a deterministic function on therecovered master key 366 and a slice name 2 of the data slice 2 as thedata identifier 358 to produce a key 2. With the encryption keygenerated, the inverse per slice security processing 202 decrypts thereceived encrypted data unit using the encryption key to recover thedata unit. For example, the CRYPTO 2 decrypts the received encrypteddata slice 2 using the key 2 to produce the data slice 2 as recovereddata 368.

Alternatively, when recovering the data 354, the key generator generatesat least a decode threshold number of encryption keys of the pluralityof encryption keys, at least a decode threshold number of CTPYTO modulesdecrypt at least a decode threshold number of received encrypted dataslices 360 to produce at least a decode threshold number of data slices,and the error decoding 2 dispersed storage error decodes the at least adecode threshold number of data slices to reproduce the data 354 asrecovered data 368.

FIG. 40C is a flowchart illustrating an example of accessing data in adispersed storage network (DSN). In particular, a method is presentedfor use in conjunction with one or more functions and features describedin conjunction with FIGS. 1-39, 40A-B, and also FIG. 40C. The methodbegins or continues at step 370 when storing the data in the DSN where aprocessing module of a computing device of one or more computing devicesof the DSN divides the data into a plurality of data units. For example,the processing module dispersed storage error encodes the data toproduce a plurality of encoded data slices as the plurality of dataunits.

The method continues at step 372 where the processing module generates aplurality of encryption keys from a master key associated with the dataand a data identifier associated with the data. The generating mayinclude obtaining the master key by generating a random number andperforming a key generating function on the random number to produce themaster key (e.g., with a sufficient number of bits). As a specificexample of generating the plurality of encryption keys, the processingmodule performs a one-way deterministic function on the master key and aplurality of data unit names to produce the plurality of encryptionkeys, where the data identifier includes the plurality of data unitnames. As another specific example of generating the plurality ofencryption keys, the processing module performs a series of one-waydeterministic functions on the master key and the data identifier toproduce the plurality of encryption keys.

The method continues at step 374 where the processing module encryptsthe plurality of data units using the plurality of encryption keys toproduce a plurality of encrypted data units. The method continues atstep 376 where the processing module sends the plurality of encrypteddata units to a first set of storage units of the DSN for storage. Themethod continues at step 378 where the processing module encodes themaster key to produce a plurality of encoded master key units. As aspecific example, the processing module performs an all-or-nothingtransformation on the master key to produce a secure master key anddispersed storage error encodes the secure master key to produce aplurality of encoded master key slices as the plurality of encodedmaster key units. As another specific example, the processing moduleperforms a Shamir secret sharing encoding function on the master key toproduce a plurality of secret master key shares as the plurality ofencoded master key units.

The method continues at the step where the processing module sends theplurality of encoded master key units to a second set of storage unitsof the DSN for storage. The first and second sets of storage units mayinclude at least one storage unit in common.

The method continues or begins, when retrieving the data from the DSN,at step 382 where the processing module receives a request to retrieve adata unit of the plurality of data units. The method continues at step384 of the processing module retrieves an encrypted data unit of theplurality of encrypted data units from a storage unit of the first setof storage units, where the encrypted data unit corresponds to the dataunit. The method continues at step 386 where the processing moduleretrieves at least some (e.g., a decode threshold number) of theplurality of encoded master key units from the second set of storageunits.

The method continues at step 388 where the processing module decodes theat least some of the plurality of encoded master key units to produce arecovered master key. The method continues at step 390 where theprocessing module generates an encryption key of the plurality ofencryption keys from the recovered master key and the data identifier.The method continues at step 392 where the processing module decryptsthe encrypted data unit using the encryption key to recover the dataunit.

The method described above in conjunction with the processing module canalternatively be performed by other modules of the dispersed storagenetwork or by other devices. In addition, at least one memory section(e.g., a non-transitory computer readable storage medium) that storesoperational instructions can, when executed by one or more processingmodules of one or more computing devices of the dispersed storagenetwork (DSN), cause the one or more computing devices to perform any orall of the method steps described above.

FIGS. 41A and 41B are a schematic block diagram of another embodiment ofa dispersed storage network (DSN) that includes the outbound distributedstorage and task (DST) processing 80 of FIG. 3, the network 24 of FIG.1, and a DST execution (EX) unit set 400. The DST execution unit set 400includes a set of DST execution units 1-7. Alternatively, the set of DSTexecution units 400 may include any number of DST execution units. EachDST execution unit may be implemented utilizing the DST execution unit36 of FIG. 1. The DSN functions to reliably store data 402 in the DSTexecution unit set 400.

FIG. 41A illustrates steps of an example of operation of the storing ofthe data, where the outbound DST processing 80 dispersed storage errorencodes the data 402 to produce one or more sets of encoded data slices1-n (e.g., where n=7). Having produced the one or more sets of encodeddata slices, the outbound DST processing 80 sends, via the network 24,the one or more sets of encoded data slices to the set of DST executionunits 1-7 for storage. At least some of the DST execution units receivea corresponding encoded data slice of the set of encoded data slices forstorage. For example, DST execution units 1, 3, 4, and 7 successfullyreceive a corresponding encoded data slice for storage within a firsttimeframe.

Each DST execution unit receiving an encoded data slice receives acorresponding one or more encoded data slices for local storage. The DSTexecution unit stores the one or more encoded data slices in the localmemory. Having stored the one or more encoded data slices, the DSTexecution unit determines a level of redundancy for at least some of theone or more encoded data slices. The level of redundancy includes noredundancy and generating a number of error coded slices from the one ormore encoded data slices. The determining may be based on one or more ofa historical availability level of the set of DST execution units, anexpected time for completion of writing of all of the encoded dataslices to the set of DST execution units, a desired level of DSTexecution unit availability, a desired level of DST execution unitretrieval reliability, and a predetermination. For example, the DSTexecution unit indicates that no redundancy is required when thehistorical availability level of the set of DST execution units isgreater than a high availability threshold level. As another example,the DST execution unit indicates that local redundancy is required whenthe expected time for completion of writing of all of the encoded dataslices to the set of DST execution units is greater than a writing timethreshold level.

Having determined the level of redundancy, the DST execution unitdispersed storage error encodes the one or more encoded data slices inaccordance with the level redundancy to produce redundancy information.For example, the DST execution unit 1 dispersed storage error encodesthe one or more encoded data slices to produce one error coded slices asthe redundancy information 1. Having produced the redundancyinformation, the DST execution unit stores the redundancy information toenable subsequent local rebuilding of the one or more encoded dataslices utilizing remaining encoded data slices of the one or moreencoded data slices and the redundancy information. The DST executionunit may issue storage information to indicate to the outbound DSTprocessing 80 whether each of the corresponding one or more encoded dataslices has been successfully stored by the DST execution unit.

FIG. 41B illustrates further steps of the example of operation of thestoring of the data 402, where the outbound DST processing 80 issuesstorage status 404 to the set of DST execution units based on receivedstorage information from one or more of the DST execution units, wherethe storage status 400 for indicates a number of favorably storedencoded data slices of a set of encoded data slices. Alternatively, orin addition to, each DST execution unit directly shares storageinformation.

Each DST execution unit determines to update the level of redundancy ofa set of encoded data slices by one or more of interpreting receivedstorage status 400 for, receiving a request, detecting that an estimatedretrieval reliability level is greater than a reliability thresholdlevel, and detecting that a storage utilization level is greater than astorage utilization threshold level. When updating a level ofredundancy, the DST execution unit determines an updated level ofredundancy based on one or more of a storage utilization level and astorage reliability factor. For example, the DST execution unitdetermines to eliminate redundancy information when the number offavorably stored encoded data slices of the set of encoded data slicesis equal to or greater than a threshold level. For instance, the DSTexecution unit determines to eliminate the redundancy information whensix of seven encoded data slices of the set of encoded data slices hasbeen successfully stored. In another instance, the DST execution unitdetermines to add more redundancy information (e.g., one or more extraerror coded slices) when less than the threshold level of encoded dataslices has been successfully stored and a timeframe of writing isgreater than a time frame threshold level. Having determined the updatedlevel redundancy, the DST execution unit updates the redundancyinformation based on the updated level redundancy. For example, DSTexecution units 1-5 and 7 delete corresponding redundancy information.

FIG. 41C is a flowchart illustrating an example of storing an encodeddata slice. The method begins or continues at step 406 where aprocessing module (e.g., of a distributed storage and task (DST)execution unit) receives one or more encoded data slices for storage.The method continues at step 408 where the processing module stores theone or more encoded data slices in one or more memories of a set ofmemories. For example, the processing module stores the one or moreencoded data slices associated with a common data object in a commonmemory. As another example, the processing module stores each encodeddata slice in a different memory.

The method continues at step 409 where the processing module determinesa level redundancy for the one or more encoded data slices. Thedetermining may be based on one or more of a predetermined level,calculating based on historical retrieval reliability levels, andcalculating based on historical storage availability levels. The methodcontinues at step 410 where the processing module generates redundancyinformation further one or more encoded data slices in accordance withthe level redundancy. For example, the processing module dispersedstorage error encodes the one or more encoded data slices to produce oneor more error coded slices as the redundancy information. As anotherexample, the processing module replicates the one or more encoded dataslices as the redundancy information. The method continues at step 412where the processing module stores the redundancy information in anotherone or more memories of the set of memories. For example, the other oneor more memories may include the one or more memories of the set ofmemories. As another example, the other one or more memories does notinclude the one or more memories.

The method continues at step 414 where the processing module determinesto update the level of redundancy. For example, the processing moduledetects a change in a required retrieval reliability level. As anotherexample, the processing module detects a threshold number of favorablystored slices of a set of encoded data slices that includes a slice ofthe one or more slices. As another example, the processing moduledetects that a storage utilization level is greater than a storageutilization threshold level.

The method continues at step 416 where the processing module determinesan updated level of redundancy based on one or more of a storageutilization level and a storage reliability level. The determiningincludes identifying an approach based on an updated acquired retrievalreliability level. The method continues at step 418 where the processingmodule updates the redundancy information based on the updated level ofredundancy. The determining includes one of indicating no redundancyinformation required, maintaining the current level of redundancy,revising upwards the level of redundancy, and revising downwards thelevel redundancy. The method continues at step 420 where the processingmodule updates storage of the redundancy information based on theupdated redundancy information. For example, the processing moduleencodes more error coded slices when the level of redundancy has beenrevised upwards. As another example, the processing module deletes allerror coded slices of the redundancy information when the determinationis no redundancy information is required.

FIG. 42A is a schematic block diagram of another embodiment of adispersed storage network (DSN) that includes a distributed storage andtask (DST) execution (EX) unit set 430, the network 24 of FIG. 1, and aredundancy module 432. The DST execution unit set includes a set of DSTexecution units 1-8 and redundancy DST execution units R1-R4 implementedat a plurality of sites. Alternatively, the set of DST execution unitsmay include any number of DST execution units and the redundancy DSTexecution units may include any number of redundancy DST executionunits. For example the DST execution unit set includes four sites, whereeach site includes two DST execution units and one redundancy DSTexecution unit.

Each DST execution unit includes one or more memories. Each DSTexecution unit may be implemented utilizing the DST execution unit 36 ofFIG. 1. The redundancy module 432 may be implemented utilizing theprocessing module 84 of FIG. 3. The redundancy module 432 may be furtherimplemented within one or more of the DST processing unit 16 of FIG. 1,the DST integrity processing unit 20 of FIG. 1, and any one or more ofthe DST execution units of the DST execution unit set. The DSN functionsto generate and store local redundancy for data stored as sets ofencoded data slices in the set of DST execution units 1-8.

In an example of operation to generate and store the local redundancy,the redundancy module 432 determines a fault domain for localredundancy, where the fault domain includes a domain over at least oneof a memory device, a plurality of memory devices, storage unitsimplemented at a common site, and a subset of the set of storage units.The determining may be based on one or more of DSN topology information,expected failure rate information, a predetermination, and a rebuildinggoal. For example, the redundancy module 432 determines a first faultdomain for the DST execution unit 1 to include a first memory. Asanother example, the redundancy module determines a second fault domainfor the DST execution unit 1 to include the first memory and a secondmemory. As yet another example, the redundancy module 432 determinesanother fault domain to include all memories of DST execution units 1and 2 at common site 1.

Having determined the fault domain for local redundancy, the redundancymodule 432 generates the local redundancy for the fault domain. Forexample, the redundancy module 432 dispersed storage error encodesslices stored in memory 1 of the DST execution unit 1 to produce one ormore error coded slices as the redundancy for the first fault domain. Asanother example, the redundancy module 432 dispersed storage errorencodes slices stored in memories 1 and 2 of the DST execution unit 1 toproduce one or more other error coded slices as the redundancy for thesecond fault domain. As yet another example, the redundancy module 432dispersed storage error encodes all slices stored in all memories of theDST execution units 1 and 2 to produce still further error coded slicesas the redundancy for the other fault domain.

Having generated the local redundancy, the redundancy module 432identifies available storage locations for storing of the localredundancy. Such available storage locations includes available storageof memory devices that are also storing the encoded data slices, theavailable memory space on memories devoted to storing local redundancy,and available storage of storage units dedicated to storing theredundancy. The identifying includes one or more of performing a lookup,initiating a query, receiving a response, identifying storage locationswith a most amount of available storage capacity, and selecting storagelocations associated with a highest level of fault tolerance.

Having identified the available storage locations, the redundancy module432 selects one or more storage locations of the available storagelocations for storage of the local redundancy. The selecting may includeone or more of rank ordering the storage locations based on therebuilding goal and expected failure correlations. For example, theredundancy module assigns a low rank ordering for a storage locationthat includes a common memory with storage of an encoded data slice andthe signs a high rank ordering for another storage location that isseparate from storage of encoded data slices.

Having selected the one or more storage locations, the redundancy module432 facilitate storage of the local redundancy and the selected one ormore storage locations. When detecting a storage failure, the redundancymodule identifies and associated fault domain (e.g., a lookup, adeveloping a correlation, interpreting the DSN topology information).Having identified the fault domain, the redundancy module 432 identifiesassociated local redundancy of the fault domain (e.g., a lookup,initiating a query, receiving a response). Having identified theassociated local redundancy, the redundancy module recovers the localredundancy (e.g., retrieves error coded slices from a memory).

Having recovered the local redundancy, the redundancy module 432corrects the storage error utilizing the recovered local redundancy. Forexample, the processing module recovers further encoded data slices of aset of encoded data slices and dispersed storage error decodes a decodethreshold number of encoded data slices that includes the recoveredlocal redundancy and at least some of the recovered further encoded dataslices to produce a recovered data segment. Having produced therecovered data segment, the redundancy module 432 dispersed storageerror encodes the recovered data segment to reproduce an encoded dataslice associated with the storage error.

FIG. 42B is a flowchart illustrating an example of storing localredundancy. The method begins or continues at step 434 where aprocessing module (e.g., of a redundancy module) determines a faultdomain for local redundancy. For example, the processing module detectsnewly stored slices, initiates the determining of the fault domain basedon dispersed storage network topology information, and stores faultdomain information that indicates identifiers of one or more memorydevices associated with the fault domain. The method continues at step436 where the processing module generates the local redundancy for thefault domain. For example, the processing module dispersed storage errorencodes stored encoded data slices associated with the fault domain toproduce one or more error coded slices as the local redundancy.

The method continues at step 438 where the processing module identifiesavailable storage locations for storing the local redundancy. The methodcontinues at step 440 where the processing module selects one or morestorage locations of the identified available storage locations. Forexample, the processing module selects a storage location with a minimalfailure correlation to the fault domain. The method continues at step442 where the processing module facilitates storage of the localredundancy in the selected one or more storage locations. The processingmodule may update the fault domain information to include an identifierof the one or more storage locations

When detecting a storage error, the method continues at step 444 wherethe processing module identifies an associated fault domain (e.g., alookup of the fault domain information). The method continues at step446 where the processing module identifies an associated localredundancy of the associated fault domain (e.g., extracted fromrecovered fault domain information). The method continues at step 448where the processing module recovers the local redundancy. For example,the processing module retrieves one or more error coded slices of thelocal redundancy from the corresponding selected one or more storagelocations extracted from the recovered fault domain information.

The method continues at 450 where the processing module corrects thestorage error utilizing the recovered local redundancy. For example, theprocessing module disperse storage error decodes the retrieved errorcoded slices of the local redundancy and one or more encoded data slicesassociated with storage error to produce a reproduced data segment,dispersed storage error encodes the reproduced data segment to produce arebuilt slice corresponding to the storage error, and stores the rebuiltslice in a memory device associated with the storage error.

FIG. 43 is a flowchart illustrating another example of storing localredundancy, which includes similar steps to FIG. 42B. The method beginsor continues with step 434 of FIG. 42B where a processing module (e.g.,of a redundancy module) determines a fault domain for local redundancy.The method continues at step 450 to where the processing moduledetermines whether to generate the local redundancy. The determining maybe based on one or more of a network loading level, a storage unitloading level, a redundancy module loading level, a redundancy modulememory availability level, initiating a query to a storage unit, andreceiving a query response. The method loops at step 452 whendetermining not to generate the local redundancy. The method continuesto step 436 of FIG. 42B when determining to generate the localredundancy.

When determining to generate the local redundancy, the method continueswith the steps 436-440 of FIG. 42B where the processing module generatesthe local redundancy for the fault domain, identifies available storagelocations for storing the local redundancy, and selects one or morestorage locations of the identified available storage locations. Themethod continues at step 454 where the processing module determineswhether to store the local redundancy. The determining may be based onone or more of a network loading level, a storage location loadinglevel, a redundancy module loading level, a redundancy module memoryavailability level, initiating a query to the one or more selectedstorage locations, and receiving a query response. The method loops atstep 454 when determining not to store the local redundancy (e.g., cachethe local redundancy). The method continues to the step 442 of FIG. 42Bwhen the processing module determines to store the local redundancy.When storing the local redundancy, the method continues with the step442 of FIG. 42B where the processing module facilitate storage of thelocal redundancy and the selected one or more storage locations.

FIGS. 44A-44C are a schematic block diagram of another embodiment of adispersed storage network (DSN) that includes a distributed storage andtask (DST) execution (EX) unit set 460, the network 24 of FIG. 1, theoutbound DST processing 80 of FIG. 3, and the inbound DST processing 82of FIG. 3. The DST execution unit set 460 includes a set of DSTexecution units 1-14. Alternatively, the set of DST execution units mayinclude any number of DST execution units. Each DST execution unitincludes the processing module 84 of FIG. 3 and at least one memorydevice (e.g., memory 88 of FIG. 3) to facilitate storage of one or moreencoded data slices. Each DST execution unit may be implementedutilizing the DST execution unit 36 of FIG. 1. Hereafter, the DSTexecution unit may be interchangeably referred to as a storage unit of aset of storage units. The DSN functions to provide access to data 462stored in the DST execution unit set. The accessing includes storing thedata 462 in the DST execution unit set and retrieving stored data fromthe DST execution unit set to produce recovered data 464.

FIG. 44A illustrates steps of an example of operation of the accessingof the data 462, where, in particular, the data 462 is stored in the DSTexecution unit set 460. The example begins or continues with theoutbound DST processing 80 determining dispersal parameters for adispersed storage error coding function, where the dispersal parametersare associated with a wide-class information dispersal algorithm (IDA)width. The dispersal parameters includes one or more of a recoverythreshold number of storage units, a recovery threshold number ofencoded data slices for storage unit, a decode threshold number, an IDAwidth, and an encoding matrix. The determining includes at least one ofretrieving the dispersal parameters and generating the dispersalparameters. The generating includes producing the dispersal parameterssuch that recovering a recovery threshold number of encoded data slicesper storage unit for a recovery threshold number of storage unitsenables data recovery. The generating may further include storing thedetermined dispersal parameters to enable subsequent recovery of thedata. For example, the outbound DST processing 80 determines thedispersal parameters such that 10 of 12 encoded data slices stored ateach of 10 of 14 storage units that are required for data recovery whenthe IDA width is 168 and the decode threshold is 100 (e.g., recoverythreshold number of storage units is 10 and the recovery thresholdnumber of encoded data slices per storage unit is 10).

Having determined the dispersal parameters, the outbound DST processing80 dispersed storage error encodes the data 462 utilizing the dispersalparameters to produce a plurality of sets of encoded data slices (e.g.,encoded data slices 1-168). In particular, a data segment of the data462 is dispersed storage error encoded to produce a plurality of encodeddata slices (e.g., one set of encoded data slices). For each set ofencoded data slices, the outbound DST processing 80 determines a numberof encoded data slices for storage in each DST execution unit such thateach storage unit of the set of storage unit stores a unique sub-set ofencoded data slices of the plurality of encoded data slices of the datasegment. For example, the outbound DST processing 80 determines thenumber of encoded data slices for storage in each DST execution unit inaccordance with a formula: number of slices per storage unit=IDAwidth/number of storage units (e.g., 168/14=12). Having determined thenumber of slices for storage in each storage unit, the outbound DSTprocessing 80 facilitate storage of the plurality of sets of encodeddata slices of the set of storage units using the number of encoded dataslices for each storage unit such that the storage units of the DSNstore the plurality of encoded data slices of the data segment. Forexample, the outbound DST processing 80 issues a set of write slicerequests 1-14, via the network 24, to the set of DST execution units1-14, where each write slice request includes, for each set of encodeddata slices, 12 encoded data slices. For instance, the outbound DSTprocessing 80 sends a unique sub-set of encoded data slices (e.g.,encoded data slices 1-12) of the plurality of encoded data slices to DSTexecution unit 1 for storage, sends encoded data slices 13-24 to DSTexecution unit 2 for storage, etc.

FIG. 44B illustrates further steps of the example of operation of theaccessing of the data 462 where the processing module 84 of each DSTexecution unit dispersed storage error encodes at least a recoverythreshold number of encoded data slices of the unique sub-set of encodeddata slices to produce a local set of encoded recovery data slices. Therecovery threshold number of encoded data slices may be equal to anumber of encoded data slices in the unique sub-set of encoded dataslices. For the example, the DST execution unit dispersed storage errorencodes 12 encoded data slices when the recovery threshold number ofencoded data slices includes 12 encoded data slices and the number ofencoded data slices of the unique sub-set of encoded data slices is 12.Alternatively, the recovery threshold number of encoded data slices isless than the number of encoded data slices in the unique sub-set ofencoded data slices. For the example, the DST execution unit dispersedstorage error encodes an encoded data slices when the recovery thresholdnumber of encoded data slices is 10 and the number of encoded dataslices in the unique sub-set of encoded data slices is 12.

Having produced the local set of encoded recovery data slices, the DSTexecution unit facilitates storage of the local set of encoded recoverydata slices. For example, each DST execution unit stores all of theencoded data slices of the local set of encoded recovery data slices ina local memory of the DST execution unit. As another example, when therecovery threshold number of encoded data slices is less than the numberof encoded data slices in the unique sub-set of encoded data slices,each DST execution unit may overwrite one or more encoded data slices ofthe unique sub-set of encoded data slices with the local set of encodedrecovery data slices. For instance, DST execution unit 1 produces thelocal set of encoded recovery data slices to include encoded data slices1-10 and error coded slices 1 and 2; and overwrites encoded data slicesof 11-12 with error coded slices 1 and 2 when encoded data slices 1-10of the local set of encoded recovery data slices are substantially thesame as received encoded data slices 1-10 in accordance with thedispersed storage error encoding of the received recovery thresholdnumber of encoded data slices (e.g., the encoding includes utilizing aunity matrix for a first decode threshold number of entries, where thedecode threshold is 10). As such, the DST execution unit 1 may utilizeerror coded slices 1-2 in conjunction with the encoded data slices 1-10of the local set of encoded recovery data slices to address a rebuildingissue where the DST execution unit 1 corrects up to at least two sliceerrors within the local set of encoded recovery data slices at a localstorage unit level of rebuilding (e.g., the DST execution unit 1performs rebuilding without accessing other storage units).

FIG. 44C illustrates further steps of the example of operation of theaccessing of the data 462, where, in particular, the store data is to beretrieved. The steps begin or continue with the inbound DST processing82 obtaining the dispersal parameters. The obtaining includes at leastone of accessing a system registry, accessing a directory, and accessinga dispersed hierarchical index. Having obtained the dispersalparameters, the inbound DST processing 82 identifies the DST executionunit set 460 associated with storage of the data 462 for retrieval. Forexample, the inbound DST processing 82 accesses a directory using a nameof the data to recover a DSN address and accesses a virtual DSN addressto physical location table using the DSN address to identify the DSTexecution unit set 460.

Having identified the DST execution unit set 460, in response to aretrieval request for the data segment associated with the plurality ofencoded data slices, the inbound DST processing 82 (e.g., a device ofthe DSN) identifies a desired sub-set of storage units of the set ofstorage units to produce an initial recovery number of storage units.The recovery threshold number of encoded data slices from the recoverynumber of storage units is approximately equal to the decode thresholdnumber of the plurality of encoded data slices, where the decodethreshold number corresponds to a minimum number of encoded data slicesof the plurality of encoded data slices that is required to recover thedata segment.

The identifying the desired sub-set of storage units includes one ormore of identifying the desired sub-set of storage units based onreliability of the storage units in the desired sub-set of storageunits, identifying the desired sub-set of storage units based ondecoding efficiency of the unique sets of encoded data slices stored bythe storage units in the desired sub-set of storage units, andidentifying the desired sub-set of storage units based on availabilityof the storage units in the desired sub-set of storage units. Forexample, the inbound DST processing 82 identifies the desired sub-set ofstorage units to include DST execution units 1-10 based on the decodingefficiency of the unique sets of encoded data slices stored by thestorage units in the desired sub-set of storage units (e.g., slicesdirectly include the data when produced by an encoding matrix thatincludes the unity matrix).

Having identified the initial recovery number of storage units, theinbound DST processing 82 identifies a storage unit of the initialrecovery number of storage units having a rebuilding issue. For example,the inbound DST processing 82 receives a slice availability informationfrom the DST execution unit set 460 that indicates DST execution unit 2has a one slice rebuilding issue, DST execution unit 4 as a two slicerebuilding issue, DST execution unit 6 has a greater than two slicerebuilding issue, DST execution unit 8 has a two slice rebuilding issue,and DST execution unit 10 has a one slice rebuilding issue. Inparticular, the inbound DST processing 82 identifies the DST executionunit 6 with the rebuilding issue (e.g., most severe).

Having identified the storage unit having the rebuilding issue, theinbound DST processing 82 determines whether the rebuilding issue iscorrectable at the local storage unit level or at a DSN level (e.g.,requiring accessing multiple storage units to produce one or morerebuilt encoded data slices). As a specific example, the inbound DSTprocessing 82 obtains DSN level rebuilding information (e.g., retrievesa list of encoded data slices to be rebuilt), interprets the DSN levelrebuilding information to identify one or more encoded data slices ofthe plurality of encoded data slices requiring rebuilding (e.g., greaterthan two slices of the encoded data slices 61-70 associated with DSTexecution unit 6), identifies the storage unit having the rebuildingissue based on the identity of the one or more encoded data slicesrequiring rebuilding (e.g., performs a lookup to identify a DSTexecution unit 6 based on slice names associated with encoded dataslices 61-70), and determines that the storage unit having therebuilding issue is capable of locally rebuilding the one or moreencoded data slices requiring rebuilding when the number of encodedrecovery data slices in the local set of encoded recovery data slices isequal to or greater than the number of encoded data slices in the one ormore encoded data slices requiring rebuilding (e.g., the number of errorcoded slices 1-2 is greater than the number of slice errors, i.e.,locally rebuild up to two slices such as for DST execution units 2, 4,8, and 10). As another specific example, the slice errors of DSTexecution unit 6 require correction at the DSN level since greater thantwo encoded data slices require rebuilding.

When the rebuilding issue is correctable at the DSN level (e.g.,exclusively or non-exclusively), the inbound DST processing 82 selectsanother storage unit from remaining storage units of the set of storageunits to replace the storage unit (e.g., DST execution unit 6) havingthe rebuilding issue that is correctable at the DSN level to produce arecovery number of storage units. The selecting the other storage unitincludes determining that the other storage unit does not have therebuilding issue or determining that the other storage unit has therebuilding issues that is correctable at the local storage unit level.As a specific example, the inbound DST processing 82 selects DSTexecution unit 11 (e.g., no rebuilding issues) as the other storage unitwhen the DST execution unit 6 is only correctable of the DSN level. Asanother specific example, the DST processing 82 initially selects any orall of DST execution units 2, 4, 8, and 10 when the correspondingrebuilding issues are correctable at the local storage unit level.

Having produced the recovery number of storage units (e.g., DSTexecution units 1-5, 7-11), the inbound DST processing 82 sends, via thenetwork 24, retrieve requests to the recovery number of storage units.For example, the inbound DST processing 82 generates a retrieve datasegment request as retrieve requests 1-5, 7-11 that includes a datasegment identifier associated with the data segment and sends, via thenetwork 24, the retrieve requests 1-5, 7-11 to the DST execution units1-5, 7-11. The inbound DST processing 82 receives encoded data slicesfrom at least some of the DST execution units of the recovery number ofstorage units (e.g., slices 1-10, rebuilt slice 13, slices 14-22, slices25-34, rebuilt slice 37, slices 38-45, rebuilt slice 46, slices 49-58,slices 73-82, rebuilt slice 85, slices 86-93 rebuilt slice 94, slices97-106, rebuilt slice 109, slices 110-118, slices 121-130=100 slices)and dispersed storage error decodes the received encoded data slices toproduce the recovered data 464 (e.g., a reproduced data segment).

When the rebuilding issue is correctable at the local level, the inboundDST processing 82 sends, via the network 24, the retrieve requests tothe initial recovery number of storage units. In response to one of theretrieve requests, the storage unit having the rebuilding issue that iscorrectable at the local level rebuilds an encoded data slice of therecovery threshold number of encoded data slices based on the local setof encoded recovery data slices to produce a rebuilt encoded data slice.For example, DST execution unit 2 rebuilds encoded data slice 13 of therebuilding issue of DST execution unit 2 to produce rebuilt encoded dataslice 13. Having produced the rebuilt encoded data slice, the storageunit having the rebuilding issue that is correctable at the local levelsends the rebuilt encoded data slice and remaining encoded data slicesof the recovery threshold number of encoded data slices to the inboundDST processing 82 (e.g., the device). For example, DST execution unit 2sends, via the network 24, rebuilt encoded data slice 13 and encodeddata slices 14-22 to the inbound DST processing 82. Having received theencoded data slices (e.g., including rebuilt encoded data slices) fromthe initial recovery number of storage units, the inbound DST processing82 dispersed storage error decodes the received encoded data slices toproduce the recovered data 464.

FIG. 44D is a flowchart illustrating an example of accessing data basedon a dispersed storage network (DSN) rebuilding issue. In particular, amethod is presented for use in conjunction with one or more functionsand features described in conjunction with FIGS. 1-39, 44A-C, and alsoFIG. 44D. The method begins at step 470 where one or more processingmodules of a set of storage units of a dispersed storage network (DSN)stores a plurality of encoded data slices, where each storage unit ofthe set of storage units stores a unique sub-set of encoded data slicesof the plurality of encoded data slices and where a data segment of datais dispersed storage error encoded to produce the plurality of encodeddata slices. For example, each storage unit stores 12 encoded dataslices when a number of storage units is 14 and an information dispersalalgorithm width associated with the dispersed storage error encoding is168.

The method continues at step 472 where each storage unit of the set ofstorage units dispersed storage error encodes at least a recoverythreshold number of encoded data slices of the unique sub-set of encodeddata slices to produce a local set of encoded recovery data slices. Forexample, the storage unit dispersed storage error encodes 12 encodeddata slices when the recovery threshold number of encoded data slices isequal to the number of encoded data slices in the unique sub-set ofencoded data slices. As another example, the storage unit dispersedstorage error encodes 10 encoded data slices when the recovery thresholdnumber of encoded data slices is less than the number of encoded dataslices in the unique sub-set of encoded data slices. When the recoverythreshold number of encoded data slices is less than the number ofencoded data slices in the unique sub-set of encoded data slices, eachstorage unit may overwrite one or more encoded data slices of the uniquesub-set of encoded data slices with the local set of encoded recoverydata slices. For example, each storage unit overwrites two encoded dataslices of the unique sub-set of encoded data slices when the recoverythreshold number of encoded data slices is 10 and the local set ofencoded recovery data slices is 12

In response to a retrieval request for the data segment, the methodcontinues at step 474 where a device of the DSN (e.g., an inbounddistributed storage and task module, a DST processing unit, a userdevice) identifies a desired sub-set of storage units of the set ofstorage units to produce an initial recovery number of storage units,where the recovery threshold number of encoded data slices from therecovery number of storage units is approximately equal to a decodethreshold number of the plurality of encoded data slices, where thedecode threshold number corresponds to a minimum number of encoded dataslices of the plurality of encoded data slices that is required torecover the data segment.

The identifying the desired sub-set of storage units includes one ormore of identifying the desired sub-set of storage units based onreliability of the storage units in the desired sub-set of storageunits, identifying the desired sub-set of storage units based ondecoding efficiency of the unique sets of encoded data slices stored bythe storage units in the desired sub-set of storage units, andidentifying the desired sub-set of storage units based on availabilityof the storage units in the desired sub-set of storage units. The methodcontinues at step 476 where the device identifies a storage unit of theinitial recovery number of storage units having a rebuilding issue.

The method continues at step 478 where the device determines whether therebuilding issue is correctable at a local storage unit level or at aDSN level. For example, the device obtains DSN level rebuildinginformation, interprets the DSN level rebuilding information to identifyone or more encoded data slices of the plurality of encoded data slicesrequiring rebuilding, identifies the storage unit having the rebuildingissue based on the identity of the one or more encoded data slicesrequiring rebuilding, and determines that the storage unit having therebuilding issue is capable of locally rebuilding the one or moreencoded data slices requiring rebuilding when the number of encodedrecovery data slices in the local set of encoded recovery data slices isequal to or greater than the number of encoded data slices in the one ormore encoded data slices requiring rebuilding. The method branches tostep 484 when the rebuilding issue is correctable at the local storageunit level. The method continues to step 480 when the rebuilding issueis correctable at the DSN level.

When the rebuilding issue is correctable at the DSN level, the methodcontinues at step 480 where the device selects another storage unit fromremaining storage units of the set of storage units to replace thestorage unit having the rebuilding issue that is correctable at the DSNlevel to produce a recovery number of storage units. The selectingincludes determining that the other storage unit does not have therebuilding issue or determining that the other storage unit has therebuilding issues that is correctable at the local storage unit level.The method continues at step 482 where the device sends retrieverequests to the recovery number of storage units such that the devicemay decode received encoded data slices from at least some of therecovery number of storage units to reproduce the data.

When the rebuilding issue is correctable at the local level, the methodcontinues at step 484 where the device sends the retrieve requests tothe initial recovery number of storage units. In response to one of theretrieve requests, the method continues at step 486 where the storageunit having the rebuilding issue that is correctable at the local levelrebuilds an encoded data slice of the recovery threshold number ofencoded data slices based on the local set of encoded recovery dataslices to produce a rebuilt encoded data slice. The method continues atstep 488 where the storage unit having the rebuilding issue that iscorrectable at the local level sends the rebuilt encoded data slice andremaining encoded data slices of the recovery threshold number ofencoded data slices to the device such that the device can dispersedstorage error decode received encoded data slices to reproduce the data.

The method described above in conjunction with the processing module canalternatively be performed by other modules of the dispersed storagenetwork or by other devices. In addition, at least one memory section(e.g., a non-transitory computer readable storage medium) that storesoperational instructions can, when executed by one or more processingmodules of one or more computing devices of the dispersed storagenetwork (DSN), cause the one or more computing devices to perform any orall of the method steps described above.

FIG. 45A is a schematic block diagram of another embodiment of adispersed storage and task (DST) execution (EX) unit 36 that includesthe DST client module 34 of FIG. 1, one or more memory groups 1-2, and alocal redundancy group 490. The one or more memory groups 1-2 eachincludes a set of memories 1-M. The local redundancy group 490 includesa plurality of memories 1-5. Alternatively, each memory group in thelocal redundancy group may include any number of memories. The DSTexecution unit 36 functions to store encoded data slices with localredundancy protection.

In an example of operation of storing encoded data slices, the DSTclient module 34 identifies one or more groups of memory devices basedon one or more common affiliations. The affiliations includes one ormore of storage of a plurality of encoded data slices associated with acommon data object, of a common manufacture, of a common model number,of a similar age, associated with a similar utilization level,associated with a similar historical performance level, associated withan estimated future performance level, and associated with a similarfailure rate. For example, the DST client module 34 identifies thememory group 1 to include the memories 1-M where the memories 1-M of thememory group 1 store encoded data slices associated with a common dataobject. As another example, the DST client module 34 identifies thememory group 2 to include memories 1-M where the memories 1-M of thememory group 2 store encoded data slices associated with another commondata object.

Having identified the one or more groups of memory devices, the DSTclient module 34, for each memory group, determines an estimated futureperformance level. The estimated future performance level includes oneor more of mean time between failure, a failure rate, and a number ofrespected failures over a rebuilding time window. Having determined theestimated future performance level, the DST client module 34 determinesa local redundancy approach based on the estimated future performancelevel and a number of memory devices of the memory group. The localredundancy approach includes dispersed storage error coding functionparameters, where the premise includes an information dispersalalgorithm width and a decode threshold number. For example, theprocessing module determines the local redundancy approach to includethe decode threshold number as the number of memory devices of thememory group and a number of redundancy slices based on the number ofpotential failures during the rebuilding time window. For instance, theDST client module 34 utilizes M as the decode threshold number andindicates to generate two error coded slices for the first memory groupand three error coded slices for the second memory group.

Having determined the local redundancy approach, the DST client module34 selects one or more groupings of encoded data slices stored in thegroup of memory devices, where each grouping includes a decode thresholdnumber of encoded data slices. For example, the processing moduleselects affiliated encoded data slices such as encoded data slices of acommon data object. For each selected grouping of encoded data slices,the DST client module 34 dispersed storage error encodes the grouping ofthe encoded data slices in accordance with the local redundancy approachto produce one or more redundancy slices. For example, the DST clientmodule 34 dispersed storage error encodes encoded data slices 1-M of thememory group 1 to produce redundancy slices A1 and A2. As anotherexample, the DST client module 34 dispersed storage error encodesencoded data slices 1-M of the memory group 2 to produce redundancyslices B1, B2, and B3.

For each redundancy encoded data slice, the DST client module 34 storesthe redundancy encoded data slice in a memory of a local redundancygroup. The storing includes storing the redundancy encoded data slicesin a common memory and storing the redundancy encoded data slices indifferent memories. For example, the DST client module 34 storesredundancy encoded data slice A1 in a first memory of the localredundancy group and stores redundancy encoded data slice A2 in a secondmemory of the local redundancy group when a highest level of retrievalreliability is desired. When detecting a storage error of an encodeddata slice of the slice grouping, the DST client module 34 rebuilds theencoded data slice utilizing the other encoded data slices of the slicegrouping and at least one of the one or more redundant encoded dataslices. For example, when detecting a storage error associated withencoded data slice 2 of memory group 2, the DST client module 34retrieves encoded data slices 1, 3-M from the memory group 2 andretrieves redundancy encoded data slice B1 from memory three of thelocal redundancy group, dispersed storage error decodes the retrievedencoded data slices to reproduce encoded data slice 2.

FIG. 45B is a flowchart illustrating an example of rebuilding andencoded data slice. The method begins or continues at step 492 where aprocessing module (e.g., of a distributed storage and task (DST) clientmodule) identifies one or more groups of memory devices based on one ormore common memory device affiliations. The identifying may include oneor more of interpreting a system registry entry, the shooting a query,and receiving a query response. For each group of memory devices, themethod continues at step 494 where the processing module determines anestimated future performance level.

The method continues at step 496 where the processing module determinesa local redundancy approach for the group of memory devices based on theestimated future performance level and a number of memory devices of thegroup of memory devices. For example, the processing module determinesnot to utilize redundancy when future performance compares favorably toa performance threshold level. As another example, the processing moduledetermines to produce the redundancy slices when detecting a first errorand further expecting a second error with a 50% probability level duringa rebuilding time window.

Having determined the local redundancy approach, the method continues atstep 498 where the processing module selects one or more slice groupingsare stored in the group of memory devices based on one or more commonslice affiliations. For example, the processing module selects slices ofa common data object. As another example, the processing module selectsslices of a common vault.

For each slice grouping, the method continues at step 500 where theprocessing module dispersed storage error encodes the slice grouping inaccordance with the local redundancy approach to produce one or moreredundancy slices. For example, the processing module matrix multipliesrows of an encoding matrix associated with redundancy slices by theslice groupings to produce the redundancy slices. For each redundancyslice, the method continues at step 502 where the processing modulestores the redundancy slice in a memory of a local redundancy memorygroup. When detecting a storage error of a slice of a slice grouping,the method continues at step 504 where the processing module rebuildsthe slice utilizing other slices of the slice grouping in the one ormore redundant slices.

FIG. 46A is a schematic block diagram of another embodiment of adispersed storage network (DSN) that includes the user device 12 of FIG.1, a storage broker unit 506, the network 24 of FIG. 1, and a pluralityof storage providers 1-5. Alternatively, the DSN may include any numberof storage providers. Each storage provider includes at least one of asub-dispersed storage network, a commercial entity providing storageresources, a private entity providing storage resources, a memorysystem, and a memory device. The storage broker unit 506 may beimplemented utilizing the distributed storage and task (DST) processingunit 16 of FIG. 1. The DSN functions to provide storage resources of oneor more storage providers to the user device 12.

In an example of operation of providing the storage resources, thestorage broker unit 506 obtains performance metrics 1-N for theplurality of storage providers. The storage metrics includes one or moreof a storage availability level, a data retrieval reliability level, adata storage type, a data access latency performance level, and a datastorage cost level. The obtaining includes at least one of receivingfrom the plurality of storage providers, receiving from the user device12, interpreting a storage record, and interpreting an error message.

Having obtained the performance metrics, the storage broker unit 506receives, via the network 24, a storage request 508 from the user device12. The storage request 508 includes one or more of a data sizeindicator, an estimated data storage duration, a required storageavailability level, a required storage retrieval reliability level, adesired cost level, a requesting entity identifier, a preferred storageprovider identifier, and a preferred dispersed storage error codingfunction.

Having received the storage request 508, the storage broker unit 506selects one or more candidate storage providers of the plurality ofstorage providers based on the performance metrics and the storagerequest. For example, the storage broker unit identifies one or morestorage providers that meet minimum requirements of the storage request(e.g., storage providers 2, 3, and 5). Having selected one or morecandidate storage providers, the storage broker unit 506 issues, via thenetwork 24, a storage bid request 510 to the selected one or morecandidate storage providers, where the storage bid request 510 includesa portion of the storage request. Having issued the storage bid request510, the storage broker unit 506 receives one or more storage bidresponses 512 from the selected one or more candidate storage providers.

Having received the storage bid responses 512, the storage broker unit506 selects at least one storage provider of the candidate storageproviders based on the storage bid responses and the storage request.For example, the storage broker unit 506 selects a storage providerassociated with a lowest cost. As another example, the storage brokerunit selects a storage provider associated with best performance. As yetanother example, the storage over unit selects a storage providerassociated with best fit for the requested dispersed storage errorcoding function.

Having selected the one or more storage providers (e.g., storageprovider 3), the storage broker unit 506 issues, via the network 24,selection information 514 to the user device 12 and to the at least onestorage provider (e.g., storage provider 3). The selection information514 includes one or more of a selected dispersed storage error codingfunction identifier, pricing information, a data size indicator, a datastorage duration indicator, the requesting entity identifier, and aselected storage provider identifier.

FIG. 46B is a flowchart illustrating an example of brokering selectionof a dispersed storage network (DSN). The method begins or continues atstep 520 where a processing module (e.g., of a storage broker unit)obtains performance metrics for a plurality of storage providers. Themethod continues at step 522 where the processing module receives astorage request from a requesting entity. The method continues at step524 where the processing module selects one or more candidate storageproviders based on the performance metrics and the storage request. Theselecting includes comparing attributes of the storage requestattributes of the performance metrics to identify one or more storageproviders where the attributes of the performance metrics comparesfavorably to the attributes of the storage request.

The method continues at step 526 where the processing module issues abid request to the selected one or more candidate storage providers. Themethod continues at step 528 where the processing module receives one ormore storage bid responses. The method continues at step 530 where theprocessing module selects at least one storage provider based on thestorage bid responses in the storage request. As a specific example, theprocessing module obtains selection criteria (e.g., received from therequesting entity, a predetermination determined based on the request ofthe responses), and identifies at least one storage bid response thatincludes attributes the compare favorably to the attributes of thestorage request in accordance with the selection criteria.

The method continues at step 532 where the processing module issuesselection information to the requesting entity and to the selected atleast one storage provider. As a specific example, the processing modulegenerates the selection information to include one or more of adispersed storage error coding function identifier, pricing information,a data size indicator, a data storage duration, a requesting entityidentifier, a storage provider identifier, a secondary storage provideridentifier, and a binding timeframe for utilization of the selectedstorage provider.

FIG. 47A is a schematic block diagram of another embodiment of adispersed storage network (DSN) that includes the network 24 of FIG. 1and a set of distributed storage and task (DST) execution units 1-n.Each DST execution unit may be implemented utilizing the DST executionunit 36 of FIG. 1. Each DST execution unit includes the DST clientmodule 34 of FIG. 1 and the memory 88 of FIG. 3. The memory 88 includesa primary memory 534 and a secondary memory 536. The primary memory 534includes a plurality of memory devices 1-M and the secondary memory 536includes another plurality of memory devices 1-N.

The DSN functions to rebuild an encoded data slice associated with astorage error, where one or more data segments are encoded to produceone or more sets of encoded data slices for storage in the set of DSTexecution units. Each DST execution unit stores a group of encoded dataslices 530 in the primary memory, where the group of encoded data slicesincludes a corresponding at least one encoded data slice of each set ofencoded data slices. For example, DST execution unit 1 stores encodeddata slices 1-M in the memory devices 1-M, where encoded data slices 1-Mare associated with each of M sets of encoded data slices associatedwith storage of a data object.

In an example of operation of the rebuilding of the encoded data slice,the DST client module 34 of the DST execution unit 1 selects thecorresponding group of encoded data slices for additional errorprotection. The selecting may be based on one or more of a probabilityof a storage error, a predetermination, an error message, a request, andidentifying a common affiliation of encoded data slices stored in theprimary memory (e.g., associated with a common data object, associatedwith a portion of a common data object, associated with two or morecommon data objects of a common vault, associated with any data objectof the common vault). For example, the DST client module 34 selects theencoded data slices associated with slice names, where the slice namesare substantially the same, except for a segment number field (e.g.,encoded data slices of the common data object).

Having selected the group of encoded data slices, the DST client module34 obtains the selected group of encoded data slices. For example, theDST client module 34 retrieves the group of encoded data slices from thememory devices of the primary memory 534. As another example, the DSTclient module 34 issues, via the network 24, a read slice request to atleast one other DST execution unit, and extracts the group of encodeddata slices from received read slice responses when the DST clientmodule 34 selects one or more encoded data slices of one or more otherDST execution units. For instance, the DST client module 34 of DSTexecution unit 1 retrieves n-r encoded data slices of a set of encodeddata slices when selecting a subset of a set of encoded data slices asthe group of encoded data slices sharing a common affiliation includingan association with a common set of encoded data slices.

Having obtained the selected group of encoded data slices, the DSTclient module 34 dispersed storage error encodes the selected group ofencoded data slices to produce one or more local redundancy slices. Forexample, the DST client module 34 encodes encoded data slices 1-M fromthe primary memory of DST execution unit 1 to produce local redundancyslices 1 and 2. Having produced the one or more local redundancy slices,the DST client module 34 determines an expected access frequency of theone or more local redundancy slices (e.g., estimated frequency ofreading, estimated frequency of updating). The determining may be basedon one or more of a probability of a storage error, a historical errorrecord, a data type indicator, a request, and an interpretation of aportion of a system registry. For example, the DST client module 34determines the expected access frequency to be lower than average whenthe probability of the storage error is less than a low storage errorthreshold level.

Having determined the expected access frequency, the DST client module34 selects a memory for storage of the one or more local redundancyslices based on one or more of the expected access frequency, costrequirements, and performance requirements. For example, the DST clientmodule 34 selects the primary memory 534 when the expected accessfrequency is greater than a high access frequency threshold level andthe primary memory includes memory devices associated with favorableexpected performance to support a higher access frequency. As anotherexample, the DST client module 34 selects the secondary memory 536 whenthe expected access frequency is less than a low access frequencythreshold level and the secondary memory includes memory devicesassociated with favorable cost and long-term storage reliability levelsto support a lower access frequency.

Having selected the memory for storage, the DST client module 34facilitates storage of the one or more local redundancy slices in theselected memory. For example, the DST client module 34 stores the localredundancy slices 1 and 2 in memory devices 1 and 2 of the secondarymemory when the selected memory includes the secondary memory. The DSTclient module 34 may facilitate activation and deactivation of thesecondary memory in accordance with a cost-saving approach (e.g., lesspower and longer service life for the member devices of the secondarymemory). For example, when storing the local redundancy slices 1 and 2in the secondary memory, the DST client module 34 initiates the storingby activating power to the secondary memory. When verifying that thestoring of the local redundancy slices has been completed, the DSTclient module 34 may deactivate the secondary memory.

When detecting a storage error associated with an encoded data slice ofthe group of encoded data slices, the DST client module 34 facilitatesretrieval of a read threshold number of encoded data slices 538 of otherencoded data slices of the group of encoded data slices and the one ormore local redundancy slices to produce retrieved slices. For example,the DST client module 34 retrieves encoded data slices from the primarymemory and local redundancy slices from the secondary memory 536 whenthe local redundancy slices are located in the secondary memory and areassociated with the encoded data slices of the primary memory. Asanother example, the DST client module 34 issues read slice requests toother DST execution units to retrieve the other encoded data slices ofthe group of encoded data slices and retrieves local redundancy slicesfrom the secondary memory 536 when the local redundancy slices arelocated in the secondary memory and are associated with the encoded dataslices in the other DST execution units. For instance, the DST clientmodule 34 receives encoded data slices 2, 3, through n-r from DSTexecution units 2, 3, through n-r and local redundancy slices 1 and 2from the secondary memory.

Having retrieved the read threshold number of encoded data slices, theDST client module 34 decodes a decode threshold number of retrievedencoded data slices to produce a rebuilt encoded data slice 540 for theencoded data slice associated with the storage error. Having producedthe rebuilt encoded data slice 540, the DST client module 34 facilitatesstorage of the rebuilt encoded data slice 540. For example, the DSTclient module 34 stores the rebuilt encoded data slice in the primarymemory 534 when the encoded data slice associated with the storage erroris associated with the primary memory. As another example, the DSTclient module 34 issues, via the network 24, a write slice request toanother DST execution unit, where the write slice request includes therebuilt encoded data slice 540, when the other DST execution unit isassociated with storage of the encoded data slice associated with thestorage error. For instance, the DST client module 34 sends, via thenetwork 24, rebuilt encoded data slice 3 to DST execution unit 3 when anencoded data slice 3 of DST execution unit 3 is associated with thestorage error.

FIG. 47B is a flowchart illustrating an example of another rebuilding anencoded data slice. The method begins or continues at step 542 where aprocessing module (e.g., of a distributed storage and task (DST) clientmodule) selects a group of encoded data slices for additional errorprotection. The method continues at step 544 where the processing moduleobtains the selected group of encoded data slices. The method continuesat step 546 where the processing module dispersed storage error encodesthe selected group of encoded data slices to produce one or more localredundancy slices.

The method continues at step 548 where the processing module determinesan expected access profile for the one or more local redundancy slices.The access profile includes one or more of estimated frequency ofreading and estimated frequency of updating. The determining may bebased on one or more of a probability of a storage error, an errorrecord, an error message, a data type indicator, an expected accessprofile based on a data type, and a request.

The method continues at step 550 where the processing module selects amemory for storage of the one or more local redundancy slices based onthe expected access profile. For example, the processing module selectsthe memory based on one or more of characteristics of available memorydevices, the expected access profile, and a performance goal.

When detecting a storage error associated with the group of encoded dataslices, the method continues at step 552 where the processing modulefacilitates retrieval of a read threshold number of encoded data slices.The read threshold is greater than or equal to a decode threshold andless than or equal to an information dispersal algorithm width. Each setof encoded data slices includes the information dispersal algorithmwidth number of slices. A decode threshold number of encoded data slicesof a set of encoded data slices is required for recovery when decodingrecovered encoded data slices to reproduce a corresponding data.

The method continues at step 554 where the processing module generates arebuilt encoded data slice using retrieved encoded data slices. Forexample, the processing module dispersed storage error decodes a decodethreshold number of retrieved encoded data slices to reproduce a datasegment, dispersed storage error encodes the data segment to produce arebuilt set of encoded data slices that includes the rebuilt encodeddata slice, and facilitates storage of the rebuilt encoded data slice ina memory associated with an encoded data slice of the storage error.

FIGS. 48A-48B are a schematic block diagram of another embodiment of adispersed storage network (DSN) that includes the outbound distributedstorage and task (DST) processing 80 of FIG. 3, the inbound DSTprocessing 82 of FIG. 3, the network 24 of FIG. 1, and a set of DSTexecution (EX) units 1-n. Each DST execution unit includes theprocessing module 84 of FIG. 3 and at least one memory. For example, theat least one memory includes a first memory (e.g., memory 1) for storageof encoded data slices and a second memory (e.g., memory 2) for storageof encoded recovery data slices (ERS). Each DST execution unit may beimplemented utilizing the DST execution unit 36 of FIG. 1. Each memorymay be implemented utilizing the memory 88 of FIG. 3. Hereafter, eachDST execution unit may be interchangeably referred to as a storage unit,the set of DST execution units may be interchangeably referred to as aset of storage units, and the inbound DST processing 82 may beinterchangeably referred to as a requesting computing device (e.g., whenin conjunction with the DST processing unit 16 of FIG. 1 or with inconjunction with the user device 14 of FIG. 1). The DSN functions toaccess data, where the accessing includes storing the data to producestored data and retrieving the stored data to produce recovered data.

FIG. 48A illustrates steps of an example of operation of the storing ofthe data to produce stored data where the outbound DST processing 80dispersed storage error encodes a plurality of data segments to producea plurality of sets of encoded data slices, where the data objectincludes the plurality of data segments. For example, the outbound DSTprocessing 80 divides data object A into Y data segments and dispersedstorage error encodes each data segment to produce Y sets of encodeddata slices 1-n. For instance, a first set of encoded data slicesincludes encoded data slices A-1-1 through A-n-1, a second set ofencoded data slices includes encoded data slices A-1-2 through A-n-2,through a Yth set of encoded data slices includes encoded data slicesA-1-Y through A-n-Y.

Having produced the plurality of sets of encoded data slices, theoutbound DST processing 80 sends, via the network 24, the plurality ofsets of encoded data slices to the set of DST execution units forstorage, where each storage unit of the set of storage units stores aunique group of encoded data slices of the plurality of sets of encodeddata slices in the first memory (e.g., one encoded data slice per set,multiple encoded data slices per set, slices associated with a commonpillar number, any other combination). For example, the outbound DSTprocessing 80 sends encoded data slices A-1-1, A-1-2, through A-1-Y tothe DST execution unit 1 for storage in the first memory as the uniquegroup of encoded data slices associated with the first storage unit whena first encoded data slice of each set of encoded data slices is to beincluded in the unique group of encoded data slices associated with thefirst storage unit.

Each storage unit receiving and storing a corresponding unique group ofencoded data slices dispersed storage error encodes at least some ofencoded data slices of the unique group of encoded data slices toproduce a local set of encoded recovery data slices. For example, theprocessing module 84 of the DST execution unit 1 dispersed storage errorencodes the unique group of encoded data slices that includes theencoded data slices A-1-1, A-1-2, through A-1-Y to produce the local setof encoded recovery data slices that includes encoded recovery dataslice (ERS) A-1-a and A-1-b.

Having produced the local set of encoded recovery data slices, eachstorage unit stores the local set of encoded recovery slices in thesecond memory. As such, improved data retrieval reliability may beprovided by storing the encoded data slices and the encoded recoverydata slices in different memories. Alternatively, the encoded dataslices and the encoded recovery data slices may be stored in a commonmemory. Having stored the encoded recovery slices, each storage unit mayrebuild errant encoded data slices of the unique group of encoded dataslices up to a number of encoded recovery data slices. For the example,the DST execution unit 1 may rebuild up to any two encoded data slicesof the encoded data slices A-1-1, A-1-2, through A-1-Y utilizing adecode threshold number of available slices of remaining encoded dataslices of the unique group of encoded data slices and the two encodedrecovery data slices A-1-a and A-1-b.

FIG. 48B illustrates steps of an example of operation of the retrievingthe stored data where the inbound DST processing 82 receives a retrievalrequest for data object A and issues retrieval requests (e.g., readslice requests) to at least a decode threshold number of storage units(e.g., storage units presumed to be storing a decode threshold number ofencoded data slices for each set of encoded data slices to enable datarecovery) of the set of storage units for the data object A. The issuingof the retrieval requests may include selecting the decode thresholdnumber of storage units. When selecting the decode threshold numberstorage units, the inbound DST processing 82 selects the decodethreshold number of storage units based on one or more of identifyingthe decode threshold number of storage units based on reliability of thestorage units in the decode threshold number of storage units,identifying the decode threshold number of storage units based ondecoding efficiency (e.g., how many errant encoded data slices, a numberof available encoded data slices of the unique group of encoded dataslices and the number of encoded recovery data slices, etc.) of theunique groups of encoded data slices stored by the storage units in thedecode threshold number of storage units, and identifying the decodethreshold number of storage units based on availability of the storageunits in the decode threshold number of storage units.

With the retrieval requests issued, the set of storage units receivesthe retrieval request for the data object. Having received the retrievalrequest, each storage unit of the decode threshold number of storageunits of the set of storage units sends, via the network 24, the uniquegroup of encoded data slices to the inbound DST processing 82 (e.g.,requesting computing device). For example, DST execution unit 2 sends,via the network 24, encoded data slices A-2-1 through A-2-Y to theinbound DST processing 82 as part of received slices 560.

Having sent the unique group of encoded data slices, one of the decodethreshold number of storage unit sends, via the network 24, at least oneencoded recovery data slice of the local set of encoded recovery dataslices to the requesting computing device (e.g., inbound DST processing82). For example, each storage unit of the decode threshold number ofstorage units determines whether the respective unique group of encodeddata slices includes an encoded data slice requiring rebuilding and theone of the decode threshold number of storage units identifies theencoded data slice requiring rebuilding in the unique group of encodeddata slices of the one of the decode threshold number of storage units.For instance, the DST execution unit 2 determines that encoded dataslice A-2-3 requires rebuilding, identifies the encoded data slice A-2-3as an errant encoded data slice, and sends, via the network 24, theencoded recovery data slice A-2-a to the inbound DST processing 82.

As another example of the sending the at least one encoded recovery dataslice, the one of the decode threshold number of storage unitsidentifies multiple encoded data slices in the unique group of encodeddata slices of the one of the decode threshold number of storage unitsthat require rebuilding and sends a unique encoded recovery data sliceof the local set of encoded recovery data slices to the requestingcomputing device for each of the multiple encoded data slices thatrequire rebuilding. For instance, the DST execution unit 1 identifiesencoded data slices A-1-2 and A-1-3 as errant encoded data slicesrequiring rebuilding and sends, via the network 24, the encoded recoverydata slices A-1-a and A-1-b to the inbound DST processing 82.

As yet another example of the sending the at least one encoded recoverydata slice, each storage unit of the decode threshold number of storageunits determines whether the respective unique group of encoded dataslices includes an encoded data slice requiring rebuilding, a second oneof the decode threshold number of storage units identifies the encodeddata slice requiring rebuilding in the unique group of encoded dataslices of the second one of the decode threshold number of storageunits, and the second one of the decode threshold number of storageunits sends at least one encoded recovery data slice of the local set ofencoded recovery data slices of the second one of the decode thresholdnumber of storage units to the requesting computing device.Alternatively, or in addition to, each storage unit of the decodethreshold number of storage units sends at least one encoded recoverydata slice of the respective local set of encoded recovery data slicesto the requesting computing device. For example, when a number ofencoded data slices of the unique group of encoded data slices comparesfavorably to the number of encoded data slices of the local set ofencoded recovery data slices (e.g., greater than a threshold number),each storage unit sends each encoded recovery data slice to the inboundDST processing 82 as some of the received slices 560.

Having received the received slices 560, the inbound DST processing 82identifies an errant encoded data slice of the unique group of encodeddata slices from the one of the decode threshold number of storageunits. The identifying the errant encoded data slice includes at leastone of receiving an indication from the one of the decode thresholdnumber of storage units (e.g., based on the identifying and indicatingby the storage units), performing an integrity check on the errantencoded data slice (e.g., indicate errant when a stored integrity valuedoes not substantially match a calculated integrity value), andidentifying the errant encoded data slice from a rebuild list (e.g.,identifying a slice name from the rebuild list that matches a slice nameof an encoded data slice of the unique group of encoded data slices).

Having identified the errant encoded data slice, the inbound DSTprocessing 82 corrects the errant encoded data slice based on remainingencoded data slices of the unique group of encoded data slices from theone of the decode threshold number of storage units and the local set ofencoded recovery data slices (e.g., at least one) from the one of thedecode threshold number of storage units to produce an updated uniquegroup of encoded data slices. For example, the inbound DST processing 82creates a rebuilt encoded data slice from the at least one encodedrecovery data slice and remaining encoded data slices of the uniquegroup of encoded data slices and replaces the errant encoded data slicewith the rebuilt encoded data slice to produce the updated unique groupof encoded data slices. For instance, the inbound DST processing 82disperse storage error encodes encoded data slices A-1-1, A-1-4 throughcapital A-1 Y, and encoded recovery data slices A-1-a and A-1-b toproduce rebuilt encoded data slices A-1-2 and A-1-3 to produce theupdated unique group of encoded data slices corresponding to the DSTexecution unit 1.

Having produced the updated unique group of encoded data slices, theinbound DST processing 82 dispersed storage error decodes the updatedunique group of encoded data slices and the unique groups of encodeddata slices from remaining ones of the decode threshold number ofstorage units to recover the data object. For example, the inbound DSTprocessing 82 disperse storage error decodes a decode threshold numberof encoded data slices of the first set of encoded data slices toreproduce the first data segment, dispersed storage error decodes adecode threshold number of encoded data slices of the second set ofencoded data slices (e.g., which may include a rebuilt encoded dataslice A-1-2) to reproduce the second data segment, dispersed storageerror decodes a decode threshold number of encoded data slices of thethird set of encoded data slices (e.g., which includes rebuilt encodeddata slices A-1-3, A-2-3, etc.) to reproduce the third data segment,etc.

Alternatively, or in addition to, the inbound DST processing 82determines that a data segment of the plurality of data segments isunrecoverable due to a corresponding set of encoded data slicesincluding less than a decode threshold number of uncorrupted encodeddata slices (e.g., based on the received encoded data slices 560, basedon interpreting a list slice responses). Having determined that the datasegment is unrecoverable, the inbound DST processing 82 sends a requestfor the local set of encoded recovery data slices from each of thestorage units of the decode threshold number of storage units andutilizes the local set of encoded recovery data slices from each of thestorage units of the decode threshold number of storage units and theunique group of encoded data slices from the decode threshold number ofstorage units to recover the data segment. For example, the inbound DSTprocessing 82 utilizes the local set of encoded recovery data slicesfrom each of the storage units of the decode threshold number of storageunits to recover the third data segment when a decode threshold numberof encoded data slices of the third data segment are unrecoverable(e.g., missing, corrupted).

FIG. 48C is a flowchart illustrating an example of reliably recoveringstored data. In particular, a method is presented for use in conjunctionwith one or more functions and features described in conjunction withFIGS. 1-39, 48A-B, and also FIG. 48C. The method begins at step 570where one or more processing modules of a set of storage units of adispersed storage network (DSN) receives a retrieval request for a dataobject, where the data object includes a plurality of data segments, andwhere the plurality of data segments is dispersed storage error encodedinto a plurality of sets of encoded data slices. Each storage unit ofthe set of storage units stores a unique group of encoded data slices ofthe plurality of sets of encoded data slices and each storage unitdispersed storage error encodes at least some of encoded data slices ofthe unique group of encoded data slices to produce a local set ofencoded recovery data slices.

The method continues at step 572 where each storage unit of a decodethreshold number of storage units of the set of storage units sends theunique group of encoded data slices to a requesting computing device.For example, the requesting computing device selects the decodethreshold number of storage units based on one or more of identifyingthe decode threshold number of storage units based on reliability of thestorage units in the decode threshold number of storage units,identifying the decode threshold number of storage units based ondecoding efficiency of the unique groups of encoded data slices storedby the storage units in the decode threshold number of storage units,and identifying the decode threshold number of storage units based onavailability of the storage units in the decode threshold number ofstorage units.

The method continues at step 574 where one of the decode thresholdnumber of storage units sends at least one encoded recovery data sliceof the local set of encoded recovery data slices to the requestingcomputing device. For example, each storage unit of the decode thresholdnumber of storage units determines whether the respective unique groupof encoded data slices includes an encoded data slice requiringrebuilding and the one of the decode threshold number of storage unitsidentifies the encoded data slice requiring rebuilding in the uniquegroup of encoded data slices of the one of the decode threshold numberof storage units. As another example, the one of the decode thresholdnumber of storage units identifies multiple encoded data slices in theunique group of encoded data slices of the one of the decode thresholdnumber of storage units that require rebuilding and sends a uniqueencoded recovery data slice of the local set of encoded recovery dataslices to the requesting computing device for each of the multipleencoded data slices that require rebuilding.

As yet another example of the sending of the encoded recovery dataslice, each storage unit of the decode threshold number of storage unitsdetermines whether the respective unique group of encoded data slicesincludes an encoded data slice requiring rebuilding, a second one of thedecode threshold number of storage units identifies the encoded dataslice requiring rebuilding in the unique group of encoded data slices ofthe second one of the decode threshold number of storage units, and thesecond one of the decode threshold number of storage units sends atleast one encoded recovery data slice of the local set of encodedrecovery data slices of the second one of the decode threshold number ofstorage units to the requesting computing device. Alternatively, or inaddition to, each storage unit of the decode threshold number of storageunits sends at least one encoded recovery data slice of the respectivelocal set of encoded recovery data slices to the requesting computingdevice.

The method continues at step 576 where the requesting computing deviceidentifies an errant encoded data slice of the unique group of encodeddata slices from the one of the decode threshold number of storageunits. The identifying the errant encoded data slice includes at leastone of receiving an indication from the one of the decode thresholdnumber of storage units, performing an integrity check on the errantencoded data slices, and identifying the errant encoded data slice froma rebuild list.

The method continues at step 578 where the requesting computing devicecorrects the errant encoded data slice based on remaining encoded dataslices of the unique group of encoded data slices from the one of thedecode threshold number of storage units and the local set of encodedrecovery data slices (e.g., at least one) from the one of the decodethreshold number of storage units to produce an updated unique group ofencoded data slices. For example, the requesting computing devicecreates a rebuilt encoded data slice from the at least one encodedrecovery data slice and remaining encoded data slices of the uniquegroup of encoded data slices and replaces the errant encoded data slicewith the rebuilt encoded data slice to produce the updated unique groupof encoded data slices.

The method continues at step 580 where the requesting computing devicedispersed storage error decodes the updated unique group of encoded dataslices and the unique groups of encoded data slices from remaining onesof the decode threshold number of storage units to recover the dataobject. Alternatively, or in addition to, the requesting computingdevice determines that a data segment of the plurality of data segmentsis unrecoverable due to a corresponding set of encoded data slicesincluding less than a decode threshold number of uncorrupted encodeddata slices, sends a request for the local set of encoded recovery dataslices from each of the storage units of the decode threshold number ofstorage units, and utilizes the local set of encoded recovery dataslices from each of the storage units of the decode threshold number ofstorage units and the unique group of encoded data slices from thedecode threshold number of storage units to recover the data segment.

The method described above in conjunction with the processing module canalternatively be performed by other modules of the dispersed storagenetwork or by other devices. In addition, at least one memory section(e.g., a non-transitory computer readable storage medium) that storesoperational instructions can, when executed by one or more processingmodules of one or more computing devices of the dispersed storagenetwork (DSN), cause the one or more computing devices to perform any orall of the method steps described above.

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “operably coupled to”, “coupled to”, and/or “coupling” includesdirect coupling between items and/or indirect coupling between items viaan intervening item (e.g., an item includes, but is not limited to, acomponent, an element, a circuit, and/or a module) where, for indirectcoupling, the intervening item does not modify the information of asignal but may adjust its current level, voltage level, and/or powerlevel. As may further be used herein, inferred coupling (i.e., where oneelement is coupled to another element by inference) includes direct andindirect coupling between two items in the same manner as “coupled to”.As may even further be used herein, the term “operable to” or “operablycoupled to” indicates that an item includes one or more of powerconnections, input(s), output(s), etc., to perform, when activated, oneor more its corresponding functions and may further include inferredcoupling to one or more other items. As may still further be usedherein, the term “associated with”, includes direct and/or indirectcoupling of separate items and/or one item being embedded within anotheritem. As may be used herein, the term “compares favorably”, indicatesthat a comparison between two or more items, signals, etc., provides adesired relationship. For example, when the desired relationship is thatsignal 1 has a greater magnitude than signal 2, a favorable comparisonmay be achieved when the magnitude of signal 1 is greater than that ofsignal 2 or when the magnitude of signal 2 is less than that of signal1.

As may also be used herein, the terms “processing module”, “processingcircuit”, and/or “processing unit” may be a single processing device ora plurality of processing devices. Such a processing device may be amicroprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on hard coding of the circuitry and/oroperational instructions. The processing module, module, processingcircuit, and/or processing unit may be, or further include, memoryand/or an integrated memory element, which may be a single memorydevice, a plurality of memory devices, and/or embedded circuitry ofanother processing module, module, processing circuit, and/or processingunit. Such a memory device may be a read-only memory, random accessmemory, volatile memory, non-volatile memory, static memory, dynamicmemory, flash memory, cache memory, and/or any device that storesdigital information. Note that if the processing module, module,processing circuit, and/or processing unit includes more than oneprocessing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the Figures. Such a memorydevice or memory element can be included in an article of manufacture.

The present invention has been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claimed invention. Further, theboundaries of these functional building blocks have been arbitrarilydefined for convenience of description. Alternate boundaries could bedefined as long as the certain significant functions are appropriatelyperformed. Similarly, flow diagram blocks may also have been arbitrarilydefined herein to illustrate certain significant functionality. To theextent used, the flow diagram block boundaries and sequence could havebeen defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claimed invention. One of average skill in the artwill also recognize that the functional building blocks, and otherillustrative blocks, modules and components herein, can be implementedas illustrated or by discrete components, application specificintegrated circuits, processors executing appropriate software and thelike or any combination thereof.

The present invention may have also been described, at least in part, interms of one or more embodiments. An embodiment of the present inventionis used herein to illustrate the present invention, an aspect thereof, afeature thereof, a concept thereof, and/or an example thereof. Aphysical embodiment of an apparatus, an article of manufacture, amachine, and/or of a process that embodies the present invention mayinclude one or more of the aspects, features, concepts, examples, etc.,described with reference to one or more of the embodiments discussedherein. Further, from figure to figure, the embodiments may incorporatethe same or similarly named functions, steps, modules, etc., that mayuse the same or different reference numbers and, as such, the functions,steps, modules, etc., may be the same or similar functions, steps,modules, etc., or different ones.

While the transistors in the above described figure(s) is/are shown asfield effect transistors (FETs), as one of ordinary skill in the artwill appreciate, the transistors may be implemented using any type oftransistor structure including, but not limited to, bipolar, metal oxidesemiconductor field effect transistors (MOSFET), N-well transistors,P-well transistors, enhancement mode, depletion mode, and zero voltagethreshold (VT) transistors.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of the various embodimentsof the present invention. A module includes a processing module, afunctional block, hardware, and/or software stored on memory forperforming one or more functions as may be described herein. Note that,if the module is implemented via hardware, the hardware may operateindependently and/or in conjunction software and/or firmware. As usedherein, a module may contain one or more sub-modules, each of which maybe one or more modules.

While particular combinations of various functions and features of thepresent invention have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent invention is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A method comprises: storing, by a set of storageunits of a dispersed storage network (DSN), a plurality of encoded dataslices, wherein each storage unit of the set of storage units stores aunique sub-set of encoded data slices of the plurality of encoded dataslices and wherein a data segment of data is dispersed storage errorencoded to produce the plurality of encoded data slices; dispersedstorage error encoding, by each storage unit of the set of storageunits, at least a recovery threshold number of encoded data slices ofthe unique sub-set of encoded data slices to produce a local set ofencoded recovery data slices; and in response to a retrieval request forthe data segment: identifying, by a device of the DSN, a desired sub-setof storage units of the set of storage units to produce an initialrecovery number of storage units; identifying, by the device, a storageunit of the initial recovery number of storage units having a rebuildingissue; determining, by the device, whether the rebuilding issue iscorrectable at a local storage unit level or at a DSN level; when therebuilding issue is correctable at the DSN level, selecting, by thedevice, another storage unit from remaining storage units of the set ofstorage units to replace the storage unit having the rebuilding issuethat is correctable at the DSN level to produce a recovery number ofstorage units; and sending, by the device, retrieve requests to therecovery number of storage units.
 2. The method of claim 1 furthercomprises: when the rebuilding issue is correctable at the local level,sending, by the device, the retrieve requests to the initial recoverynumber of storage units; in response to one of the retrieve requests,rebuilding, by the storage unit having the rebuilding issue that iscorrectable at the local level, an encoded data slice of the recoverythreshold number of encoded data slices based on the local set ofencoded recovery data slices to produce a rebuilt encoded data slice;and sending, by the storage unit having the rebuilding issue that iscorrectable at the local level, the rebuilt encoded data slice andremaining encoded data slices of the recovery threshold number ofencoded data slices to the device.
 3. The method of claim 1 furthercomprises: the recovery threshold number of encoded data slices is equalto a number of encoded data slices in the unique sub-set of encoded dataslices.
 4. The method of claim 1 further comprises: the recoverythreshold number of encoded data slices is less than a number of encodeddata slices in the unique sub-set of encoded data slices.
 5. The methodof claim 4 further comprises: overwriting, by each of the storage units,one or more encoded data slices of the unique sub-set of encoded dataslices with the local set of encoded recovery data.
 6. The method ofclaim 1, wherein the identifying the desired sub-set of storage unitscomprises one or more of: identifying the desired sub-set of storageunits based on reliability of the storage units in the desired sub-setof storage units; identifying the desired sub-set of storage units basedon decoding efficiency of the unique sets of encoded data slices storedby the storage units in the desired sub-set of storage units; andidentifying the desired sub-set of storage units based on availabilityof the storage units in the desired sub-set of storage units.
 7. Themethod of claim 1, wherein the determining whether the rebuilding issueis correctable at the local storage unit level or at the DSN levelcomprises: obtaining DSN level rebuilding information; interpreting theDSN level rebuilding information to identify one or more encoded dataslices of the plurality of encoded data slices requiring rebuilding;identifying the storage unit having the rebuilding issue based on theidentity of the one or more encoded data slices requiring rebuilding;and determining that the storage unit having the rebuilding issue iscapable of locally rebuilding the one or more encoded data slicesrequiring rebuilding when the number of encoded recovery data slices inthe local set of encoded recovery data slices is equal to or greaterthan the number of encoded data slices in the one or more encoded dataslices requiring rebuilding.
 8. The method of claim 1, wherein theselecting the other storage unit comprises: determining that the otherstorage unit does not have the rebuilding issue; or determining that theother storage unit has the rebuilding issue that is correctable at thelocal storage unit level.
 9. The method of claim 1 further comprises:the recovery threshold number of encoded data slices from the recoverynumber of storage units is approximately equal to a decode thresholdnumber of the plurality of encoded data slices, wherein the decodethreshold number corresponds to a minimum number of encoded data slicesof the plurality of encoded data slices that is required to recover thedata segment.
 10. A non-transitory computer readable storage mediumcomprises: at least one memory section that stores operationalinstructions that, when executed by one or more processing modules ofone or more computing devices of a dispersed storage network (DSN),causes the one or more computing devices to: store, by a set of storageunits of the DSN, a plurality of encoded data slices, wherein eachstorage unit of the set of storage units stores a unique sub-set ofencoded data slices of the plurality of encoded data slices and whereina data segment of data is dispersed storage error encoded to produce theplurality of encoded data slices; dispersed storage error encode, byeach storage unit of the set of storage units, at least a recoverythreshold number of encoded data slices of the unique sub-set of encodeddata slices to produce a local set of encoded recovery data slices; andin response to a retrieval request for the data segment: identify, by adevice of the DSN, a desired sub-set of storage units of the set ofstorage units to produce an initial recovery number of storage units;identify, by the device, a storage unit of the initial recovery numberof storage units having a rebuilding issue; determine, by the device,whether the rebuilding issue is correctable at a local storage unitlevel or at a DSN level; when the rebuilding issue is correctable at theDSN level, select, by the device, another storage unit from remainingstorage units of the set of storage units to replace the storage unithaving the rebuilding issue that is correctable at the DSN level toproduce a recovery number of storage units; and send, by the device,retrieve requests to the recovery number of storage units.
 11. Thenon-transitory computer readable storage medium of claim 10 furthercomprises: the at least one memory section stores further operationalinstructions that, when executed by the one or more processing modules,causes the one or more computing devices of the DSN to: when therebuilding issue is correctable at the local level, send, by the device,the retrieve requests to the initial recovery number of storage units;in response to one of the retrieve requests, rebuilding, by the storageunit having the rebuilding issue that is correctable at the local level,an encoded data slice of the recovery threshold number of encoded dataslices based on the local set of encoded recovery data slices to producea rebuilt encoded data slice; and sending, by the storage unit havingthe rebuilding issue that is correctable at the local level, the rebuiltencoded data slice and remaining encoded data slices of the recoverythreshold number of encoded data slices to the device.
 12. Thenon-transitory computer readable storage medium of claim 10 furthercomprises: the recovery threshold number of encoded data slices is equalto a number of encoded data slices in the unique sub-set of encoded dataslices.
 13. The non-transitory computer readable storage medium of claim10 further comprises: the recovery threshold number of encoded dataslices is less than a number of encoded data slices in the uniquesub-set of encoded data slices.
 14. The non-transitory computer readablestorage medium of claim 13 further comprises: the at least one memorysection stores further operational instructions that, when executed bythe one or more processing modules, causes the one or more computingdevices of the DSN to: overwrite, by each of the storage units, one ormore encoded data slices of the unique sub-set of encoded data sliceswith the local set of encoded recovery data.
 15. The non-transitorycomputer readable storage medium of claim 10, wherein the one or moreprocessing modules functions to execute the operational instructionsstored by the at least one memory section to cause the one or morecomputing devices of the DSN to identify the desired sub-set of storageunits by one or more of: identifying the desired sub-set of storageunits based on reliability of the storage units in the desired sub-setof storage units; identifying the desired sub-set of storage units basedon decoding efficiency of the unique sets of encoded data slices storedby the storage units in the desired sub-set of storage units; andidentifying the desired sub-set of storage units based on availabilityof the storage units in the desired sub-set of storage units.
 16. Thenon-transitory computer readable storage medium of claim 10, wherein theone or more processing modules functions to execute the operationalinstructions stored by the at least one memory section to cause the oneor more computing devices of the DSN to determine whether the rebuildingissue is correctable at the local storage unit level or at the DSN levelby: obtaining DSN level rebuilding information; interpreting the DSNlevel rebuilding information to identify one or more encoded data slicesof the plurality of encoded data slices requiring rebuilding;identifying the storage unit having the rebuilding issue based on theidentity of the one or more encoded data slices requiring rebuilding;and determining that the storage unit having the rebuilding issue iscapable of locally rebuilding the one or more encoded data slicesrequiring rebuilding when the number of encoded recovery data slices inthe local set of encoded recovery data slices is equal to or greaterthan the number of encoded data slices in the one or more encoded dataslices requiring rebuilding.
 17. The non-transitory computer readablestorage medium of claim 10, wherein the one or more processing modulesfunctions to execute the operational instructions stored by the at leastone memory section to cause the one or more computing devices of the DSNto select the other storage unit by: determining that the other storageunit does not have the rebuilding issue; or determining that the otherstorage unit has the rebuilding issue that is correctable at the localstorage unit level.
 18. The non-transitory computer readable storagemedium of claim 10 further comprises: the recovery threshold number ofencoded data slices from the recovery number of storage units isapproximately equal to a decode threshold number of the plurality ofencoded data slices, wherein the decode threshold number corresponds toa minimum number of encoded data slices of the plurality of encoded dataslices that is required to recover the data segment.